SFF Loyalty Rating Report


As a thought experiment I wanted to devise a way of comparing wildly different series within the amorphous genres of Science Fiction, Fantasy, and Urban Fantasy (hereafter abbreviated ‘SFFUF’). Namely, how loyal are each series’ reader base? Could I devise a “Loyalty Rating for SFFUF series?

Of course I can! All I needed was a data source, Excel, and enough obsession to get it done! Enter Goodreads and their intense amount of user-submitted data. By looking at the number of ratings for series across the SFFUF genres, we can quickly get a sense of how many readers stick through any given series to the end or give up after the first book. Thanks to the elegance of mathematics, we can construct a system in which one can compare pop culture titans like Harry Potter and A Song of Ice and Fire to genre darlings like The Malazan Book of the Fallen or niche series like Shadows of the Apt. This metric won’t be about the most readers but the most dedicated readers.

Below is the first iteration of a report on the reader metrics of a large selection of SFFUF book series. For now the focus is on establishing a base of data, with the Loyalty Rating as the central metric.

Here’s a link to a public Google Docs version of the data set for you to reference. I’m assuming you are.



It was immediately obvious that I had to split trilogies away from longer series. With only three books in the entire series (or three books currently released) there aren’t enough data points to establish proper comparison between the two classes of series length.

The Trilogy Loyalty Rating: It is a simple weighted grade of 40% their retention rate of readers from book one to book two (The Hook Rating) and 60% of reader retention rate from book two to book three (known as Loyalist Completion). This emphasizes the completion of invested readers without discounting the importance of hooking people with book one.

The average Loyalty Rating for Trilogies is 67.04%

Top 10 Trilogies by Loyalty Rating

  1. 96.18% – The Tawny Man by Robin Hobb
  2. 94.40% – Void by Peter F. Hamilton
  3. 93.08% – The Fionavar Tapestry by Guy Gavriel Kay
  4. 92.70% – Liveship Traders by Robin Hobb
  5. 92.21% – The Riftwar Saga by Raymond E. Feist
  6. 91.68% – The Black Magician by Trudi Canavan
  7. 91.36% – Age of the Five by Trudi Canavan
  8. 90.91% – Wolfblade by Jennifer Fallon
  9. 90.28% – Abhorsen by Garth Nix
  10. 89.17% – Darkest Powers by Kelley Armstrong

The ten trilogies with the most loyal readers, though you might as well call it the fantasy top ten briefly interrupted by Peter F. Hamilton. Already we see Robin Hobb as a queen of reader loyalty, with two trilogies in the top ten. Her other series also score above the 70% mark, consistently above average, often well above. Trudi Canavan has similar levels of consistency across her series. The rest of the top ten aren’t terribly surprising. All are well-regarded authors with fans who adore their work, even if none are among the biggest names in SFFUF. This lack of huge star power is key to scoring high. The more popular a series gets, the more likely its first book will be flooded with readers who do not continue the series.

A common feature of all high-ranking trilogies is near-zero reader loss between books 2 and 3, the avoidance of the dreaded sophomore slump that may drive initially loyal readers toward apathy over finishing a trilogy. Most of the top 10 actually have Loyalist Completion Rates above 100%. This is acceptable, as it compensates for book 2’s data being, perhaps, underreported. After all, what kind of maniac would read books 1 and 3 of a trilogy? Consider it extra credit for near-100% read through rates.

Trilogies are ruled by age. Despite their well-defined and accessible length, the more recent a series ended, the lower its loyalty rating. This makes sense. After all, to-read lists are overstuffed with modern series and the third book of a trilogy that you like but aren’t wholly addicted to can wait while you attend to higher priority targets. The average Loyalty of a trilogy with its last release in 2012-2014 is 54.66%, over 12% lower than the population average. Loyalty ratings will rise over time as a series reaches paperback price range, it’s more casual fans catch up, and consensus over the series’ overall quality percolates through word of mouth.

Trilogy Dist

Aww, the distribution isn’t very normal. Always disappointing not to find that common piece of elegance, but oh well. The Loyalty calculation favors completion over the first impression, and with Trilogies’ lower barrier to completion, the grades should skew high and disperse over a wide range rather than wholly collecting in the middle. Still, there is something to be said for any trilogy that scores an “A”, the result of a high percentage of solidly hooked readers.

For those wondering, the sole trilogy with a grade less than 30% is The Forever War by Joe Haldeman, rocking an astonishing 19.87%. For many of you this may be the first time you heard The Forever War, something of a Sci-fi classic, had sequels. Therein lies the cause of its low grade.



I’m defining Epics as any series with four or more books, even though many trilogies could be considered ‘epic’. The Epic Loyalty Rating is a little more complicated than that of trilogies. It’s still a weighted grade composed of the following three ratings.

30% of the Hook Rate between books one and two.
40% of the Loyalist Completion, the percentage of book two readers, considered the Loyalist ‘core’ of a series, who complete the series. Further, this value receives a scaling extra credit multiplier based on the number of books in the series. This credit starts at 1.05 at book four and scaling up to 1.5 at thirteen or more books.
30% is the average percentage of loyalists retained between each entry of the series. This is known as the In-Series Retention rate. Capital R-Retention. Not confusing at all.

Thus: Epic Loyalty Rating = Hook Rate * 0.3 + Loyalist Completion * Length Credit * 0.4 + In-Series Retention * 0.3.


The average Loyalty Rating for Epic series is 61.55%.

Top 10 Epic by Loyalty Rating

  1. 94.38% – Codex Alera by Jim Butcher
  2. 89.24% – Sparhawk by David Eddings
  3. 89.20% – Harry Potter by J.K. Rowling
  4. 86.61% – Bio of a Space Tyrant by Piers Anthony
  5. 85.87% – Vorkosigan Saga by Lois McMaster Bujold
  6. 84.49% – Vatta’s War by Elizabeth Moon
  7. 84.09% – The Lost Fleet by Jack Campbell
  8. 83.46% – The Rigante by David Gemmell
  9. 81.49% – The Serrano Legacy by Elizabeth Moon
  10. 81.08% – Otherland by Tad Williams

Well. That’s certainly a strange top 10 list.

The top three here aren’t surprising. Butcher, Eddings and Rowling are compulsively readable authors. The power of Harry potter cannot be denied as even with a brutal (and surprising) drop-off of readers between books one and two, the rest of that series has effectively zero loss of readers between books two and seven. A consistent, loyal core is the key to scoring high here. The Vorkosigan Saga is incredibly long (15+ books) but its readers have stuck with it, leaving a steady number of ratings all the way up to the most recent entries.

Once again, with due respect to an exceptional boy wizard, this top 10 list is devoid of huge mainstream and classic series. Well known or prolific, certainly, but not mega popular. Within this particular Loyalty rating system, book series cannot achieve survive too much popular attention, either from genre readers or the general public. Every classic series or recent book-to-film/TV adaptation has a surge of ratings on their first entry and a steep nose dive to the second.

Science Fiction doubly suffers from this. Almost all of the iconic and classic sci-fi series only display classic numbers in their first installment. Dune, Ender’s Game, Hitchhiker’s Guide, A Wrinkle in Time. All are known primarily by their first books, and not their continuing series.

Epic Dist

Mmm, now that’s what I like to see. Epic length series have a lot going against them in this particular framework, creating something of a wall in the 60s that only series with consistent and dedicated readers can punch through.


Global Data

Let’s smash it all together and see what happen, yeah?

Loyalty Summary Chart

.The Clickbait takeaway: Fantasy Readers are either more loyal or simply more patient with their chosen series than other genres. Or perhaps more easily addicted…?

When looking at the gender of the author, the divide is fairly mild overall and in Fantasy. In Sci-Fi, it goes back to many of the top stand-outs being female-authored dark horse series and the high number of male-authored classic series with low hook rates. Aside from A Wrinkle in Time, Sci-fi classics and their associated lower series Loyalty Rates are an almost exclusively male domain. Urban Fantasy’s split swings the other way: the subgenre’s stars and standouts both skew toward female authors, particularly when you get into the YA and Paranormal Romance sub-sections.

Trilogy data by genre has Urban Fantasy with a considerable drop below the average, but currently the data set is under represented here, with only 10 UF trilogies included. Even more so than Sci-Fi and Fantasy, Urban Fantasy series tend to charge right on by having only three entries.


Notes on Methodology and Data Set

  • This report consists of 225 Science Fiction, Fantasy, and Urban Fantasy series. YA series are acceptable. Urban Fantasy titles that are more Paranormal Romance are accepted, but were not a priority in the initial harvest.
  • Rating Numbers were taken on November 18th, 2014.
  • Only series with three or more released, novel length entries are included.
  • Series based on licensed material aren’t included with the one exception of the Star Wars Thrawn Trilogy because my 13 year old self wouldn’t allow its exclusion. Future editions of this report may be more inclusive of such series.
  • Only series with less than 16 entries are included at this time. Further, the emphasis is on series with strong internal continuity. Series like Discworld and Pern and Redwall are unmanageably large.
  • The Goodreads rating data must make sense. Any series that has spurious data (ex: Book 1:30K, Book 2:22K Book 3: 50K Book 4: 38K….) will be excluded. See: David Edding’s Belgariad and Malloreon.
  • The latest release of a series must have had some time to be read by the series’ hardcore fans. For this report, anything released after early August 2014 was excluded and calculations were based on the previous entry of the series. Any future updates will have a fixed, consistent cut-off date.
  • Goodreads-related caveats
    • As many Goodreads Authors know, the site’s data can be a little quirky. Sometimes a book’s numbers will freeze for days, only to have the system flush out hundreds of new updates at once. For some series, there seems to be significant chunks of missing data, which led to the exclusion of some classic series from the report.
    • Any mention of a series’ ‘reader base’ should be understood as ‘Goodreads users self-reporting their completion of books’. Goodreads, while a very large user base, has its own skews and biases. Fortunately, the calculations normalize out the demographics and tastes of Goodreads’ users.



I consider this report phase one of a periodically updated piece. I will be updating the data in the first week of January, regardless of any response. It’s a fun diversion, the union of many of my interests in a single project. Once again, you can find the full set of SFFUF series and their ratings and metrics in the public Google Doc here: https://docs.google.com/spreadsheets/d/1of3Ykfe8tg9ENmlMKLbz4iO5W5fLLtLnfKV-m2iqUGU/edit?usp=sharing

You can find my own Goodreads account here. Please proceed to make assumptions of my biases based on my personal fantasy/sci-fi shelves. You can channel any questions or rage over your favorite series being excluded to my Twitter account or the contact info tab on this website.