* Character fan. Follows the books about one character/group of characters, may not read other books by same author.
* Setting fan. Follows the books in a particular setting. May not read other books by same author.
* Story arc fan: Reader will follow the story arc through a trilogy or series, but may not read more books in a new story arc about the same characters/setting.
* Genre fan. Reads author's works in a particular genre, but not in other genres.
* Theme/review based. Readers who pick up the author's works based on theme, or reviews. This group has tastes with regards to the author that are harder to slot into the usual groups, and the author's works sometimes suit those tastes and sometimes don't.
* Former fan: Reader followed one of the patterns above, but for one reason or another stopped. "Former fans" aren't necessarily people who stopped reading an author entirely. They might be people who bought the first five books of a ten+ book series, and then lost interest in that series but are still interested in one or more other works by the same author.
* Author fan. Reads everything the author writes, regardless.
* Casual. Picked up one book, may or may not ever get another by that author.
I don't mean for these categories to be "each person is one of these types of readers". I came up with these categories because they are all groups that I fall into for different authors.
Examples where I am:
Character Fan: P. B. O'Brian's Aubrey/Maturin books, Jim Hines' Libriomancer books.
Setting Fan: K.J. Charles, "Charm of Magpies" setting.
Author Fan: Diana Wynne Jones, Lois McMaster Bujold, Bard Bloom, Terry Pratchett, Brandon Sanderson
Story Arc Fan: J.K. Rowling's 7-book "Harry Potter" series.
Theme Fan: MCA Hogarth, Walter Jon Williams
Casual: Neil Gaiman (I started reading Neil Gaiman's Sandman in 1990 or so, and I've read at least three of his other books and a few short stories. I really liked Sandman at the time, but somehow none of his books that I tried have made me a fan of his non-comics work. I don't hate them, just not that into him.)
Other: Courtney Milan. I've read eight or so novels/novellas by her, and I expect to read more. But she has a bunch of books out that I haven't yet bought or read, and I don't have any plans to go get more.
Former Fan: These are all cases where I read at least three books but stopped, even though more have come out:
George R.R. Martin: Wildcards
George R.R. Martin: Song of Ice and Fire
David Weber: Honor Harrington
L. K. Hamilton: Anita Blake
Piers Anthony (I was young and foolish. Seriously, he really does think like a teenager and anecdotal evidence shows he is inexplicably appealling to kids between 10-17 or so, then they grow up and can't really remember why. If you're one of those people who still has nostalgic fondness for one of his books, DO NOT GO BACK AND READ IT. You will have regrets.)
In a lot of these cases, it's hard to pin down why my reading habits are the way they are. I liked Charles' first three "Magpies" books and adored the spinoff, Jackdaw, but haven't sought out any of her other books in different series anyway.
In some cases, it was series fatigue: I stopped reading new Pern books long before I stopped reading McCaffrey entirely. I think that "historical romance fatigue" may be why I haven't read more books Courtney Milan. I liked the last historical romance I read by her, but I had a strange sense of 'sameness' while reading it that made me not want to get another one. I don't regard that as a "former fan" scenario because I'm pretty sure I will read more of her work in coming years.
Part of why I'm thinking about this is that it's so complicated. The "thousand true fans" theory hinges on the idea that you can hook people on your name, and they'll buy whatever you write. The "series sell" strategy hinges on "readers become hooked on a character or setting, and they won't necessarily read works with a different theme". And yet I know in my own experience that there are cases where I've read several books in a series and then quit that series -- but will still read other works by that author. As well as cases where I read a series but not other works by that author. OTOH, the "series sells" philosophy obviously works for most of the market, if not for me. Hamilton and Weber are very successful, 20+ books on in their series. And I've spoken to authors who kept writing in a successful series for the money, and yes, it worked for them better than branching out did. Even though they were sick of writing that series.
I don't really have any conclusions from this, just musings and questions. Do you have any categories I missed? Do you find yourself more likely to fall into a particular pattern with most authors, or does it vary wildly for you too?