I don't have a big physical library, for three reasons:

1. Lack of space.
2. I read books almost exclusively on my Kindle now.
3. There are very few books that I'll ever go back and read again. But that being said, I do have hard copies of many if my favorites.

As far as genre, I'm pretty eclectic. I like a bit of everything. I might even like romance novels if I ever read one. :) But I don't read non-fiction books, because they're boring to me.