I couldn't resist joining in this parlour game, (also here and here) - how many books by or about an author have you got? My own (partial list with reasons) includes -:
Anthony Burgess - 26 (he was prolific, I picked them up cheap, I once thought of doing a PhD on him, he's in Manchester where I live, I've only read a handful of them... but one of these days.)
F. Scott Fitzgerald - 16 (inc. 2 versions of the letters, 3 versions of Gatsby, one that is all Zelda, one that is Zelda and him, a couple of biographies, his 2nd wife's memoir...okay, okay, I'm a fan!)
Mary McCarthy - 14 (ditto Burgess apart from the PhD and Manchester bits, but she is good... and gets me out of the "no women on the list" problem others have had...)
John Ashbery - 12 (though "the mooring of starting out" is 5 books in one so I should get bonus points)
D.H. Lawrence - 11 (inc. a biog, selected letters etc.)
Bruce Chatwin - 10 (inc. 2 biographies and all that he ever published!)
William Burroughs - 10 (inc. a book of interviews, a biography, 2 career-spanning anthologies.)
George Eliot - 9 (inc. 2 biographies and 2 versions of Silas Marner for some reason)
Martin Amis - 9 (kind of given up buying them all, but will fill in the gaps if I see them cheap-ish, and half a dozen by Kingsley probably tips the "family" balance!)
Michael Moorcock - 8 (although they are mostly different versions/variations on his Jerry Cornelius collection which I've been trying to pick up, and its a complex bibliography!)
Philip Roth - 8 (though Zuckerman bound is 3 books in 1)
I'd guess that Andre Dubus, Don DeLillo and perhaps even David Foster Wallace might one day make the list, but I'm in no hurry, my collection being generally wider than it is deep. I think its useful though - one's reading isn't accumulated instantly, but over time, some enthusiasms seem naive now, other's have grown greater as time goes on, others are yet to flourish. I would like, when all's said and done to be able to map these co-ordinates of my tastes, interests, and obsessions, and see that yes, my own artistic sensibility was created there, somehow.