The Longest Book Series: Fifteen Series Ranked by Book Count

Readers ask about the longest book series all the time, and the honest answer depends on how you count. A list of world records would need word counts and decades of sales research. However, we have neither.

Instead, we have a structured catalogue of more than a thousand series. So this guide ranks the longest series in that catalogue by number of books. It is a catalogue ranking, not a world record.

How we ranked the longest book series

We sorted every series page on the site by its book count. Then we checked each entry’s status and start year. We also checked how many counted books carry a publication date before today.

That last check matters. Some series list a book dated after today, or a book whose date we cannot place. In those cases we show both numbers, so you can see which titles are dated before today and which are not.

What the ranking does not cover

This list does not measure word count or page count. A series of short books can have many titles and still be quick to finish. Meanwhile, a series with fewer, longer novels may take far more reading time.

We also leave out author-wide groupings that are not a single series. In addition, we keep Magic Tree House Fact Tracker as its own entry because our catalogue treats it as a separate series. Therefore, every count here depends on where the catalogue draws the series boundary.

A note on status and dates

“Ongoing” means new books may still appear. “Completed” means the series has ended, according to our catalogue. For ongoing series, we give only the start year because the end is still open.

The longest series, ranked by book count

Here are the fifteen longest series in our catalogue as of October 9, 2026. Below the table, each series name links to its full reading order.

Rank	Series	Books counted	Published	Status	Started
1	Geronimo Stilton	86	84	Ongoing	2004
2	In Death	75	75	Ongoing	1995
3	Stone Barrington	69	67	Ongoing	1991
4	Magic Tree House	67	67	Ongoing	1992
5	Goosebumps	62	62	Completed	1992
6	Spenser	55	54	Ongoing	1973
7	The Horus Heresy	54	54	Completed	2006
8	Warriors	51	51	Ongoing	2003
9	Fear Street	49	49	Completed	1989
9	Xanth	49	48	Ongoing	1977
11	Jack Ryan	44	44	Ongoing	1984
11	Magic Tree House Fact Tracker	44	44	Ongoing	2000
13	Discworld	41	41	Completed	1983
13	Hercule Poirot	41	41	Ongoing	1920
13	Alex Delaware	41	40	Ongoing	1985

Ties share a rank. Our catalogue supplies the counts, and they can shift when we refresh it each week.

The Published column counts books with a catalogue date before today. Geronimo Stilton, Spenser, Xanth and Alex Delaware each include one title with only a 2026 year, so we cannot say whether it is out. Geronimo Stilton also counts one unconfirmed title with no date, and Stone Barrington’s last two titles are dated after today.

The top five in more detail

The leaders show how different long series can be. For example, some are filed under children’s fiction, while others are crime novels.

Geronimo Stilton: 86 books counted

Geronimo Stilton tops the table. Our catalogue counts 86 books, and 84 carry a publication date before today. One more has only a 2026 year, so we cannot say whether it is out. The 86th is an unconfirmed title with no release date, so we do not count it as released.

The series is ongoing and began in 2004. Elisabetta Dami created it. Our catalogue also notes that the books are mostly self-contained, so you can start with almost any title.

In Death: 75 books

In Death is the longest mystery series in the table. All 75 counted books have reached shelves. The series began in 1995 and is still ongoing.

J. D. Robb writes it. Because it sits in the mystery category, you can browse similar shelves in our mystery genre hub.

Stone Barrington: 69 counted, 67 published

Stone Barrington is a good example of why we show two numbers. The catalogue counts 69 books, but only 67 carry a publication date before today. It lists the other two with later dates, 17 November 2026 and 2 March 2027, so treat both as upcoming.

Stuart Woods created it and is credited on 64 of the 69 books. Brett Battles is credited as continuation author on the six latest entries, starting with Near Miss, the one book that credits both. The series began in 1991 and remains ongoing.

Magic Tree House: 67 books

Magic Tree House has 67 published books and began in 1992. Mary Pope Osborne writes it. Moreover, the series is ongoing.

There is also a companion line, and Magic Tree House Fact Tracker adds 44 children’s non-fiction books. We rank it separately, since our catalogue lists it as its own series.

Goosebumps: 62 books, completed

Goosebumps is the longest completed series in the table. Its 62 books ran from 1992 to 1997, according to our catalogue. Therefore, it offers a finished run that you can read start to finish.

R. L. Stine wrote it. If you want more like it, our guide to series like Goosebumps lays out the criteria we use for suggestions.

Longest series by genre

A single ranking hides the pattern underneath it. In the table, mystery is the most common genre label, with five of the fifteen. That reflects this catalogue, not the whole book world.

Mystery and crime

Mystery is the busiest genre in the table. For instance, Spenser has 55 books and began in 1973. Robert B. Parker created it and is credited on 41 of the 55 books. Ace Atkins, Mike Lupica and Helen Brann are credited on continuation entries.

Hercule Poirot has 41 books and began in 1920, which gives it the oldest start year in the table. Likewise, Alex Delaware reaches 41. Browse more in the mystery genre hub.

Fantasy and science fiction

Warriors has 51 books and Xanth has 49. Both are ongoing. In contrast, The Horus Heresy has 54 books and is finished.

Discworld is the standout completed fantasy run, with 41 books from 1983 to 2015. Terry Pratchett wrote it. For finished fantasy of every length, see our list of completed fantasy series, or browse the fantasy genre hub.

Thrillers and horror

Jack Ryan has 44 books and is ongoing. By contrast, Fear Street has 49 books and ended after a run from 1989 to 1997. Goosebumps and Fear Street share an author, R. L. Stine. For more, visit the horror genre hub.

Children’s series

Here is how the catalogue files four of these series. Geronimo Stilton is filed under children’s fiction, Magic Tree House under adventure and Goosebumps under horror. Magic Tree House Fact Tracker is filed under children’s nonfiction. Goosebumps’ own series page gives an age of roughly 7 to 11. You can find more on our children’s genre hub.

Should you start a very long series?

Long series can feel intimidating. However, length alone should not stop you. In fact, many of these series work as a run of linked but self-contained stories.

First, check whether the series has a strict order. Then decide whether you care about the order books were published or the order events happen. Our explainer on publication order versus chronological order covers that choice in detail.

Second, think about finish lines. A completed series, such as Goosebumps or Discworld, gives you a clear ending. If you prefer shorter commitments, try our guide to completed trilogies and duologies.

Finally, if you like crime thrillers and want to branch out, see our editorial picks in authors like James Patterson. Those are our own suggestions, and the post states the criteria.