@chai2,
We do the library too -- we go every couple of weeks and get a bagful for sozlet.
I usually get my book club books at the library since they aren't ones I necessarily want to hold on to, but I absolutely LOVE recalling a certain passage, going crazy trying to remember it, then walking right up to the book, paging through and finding the passage. One of life's great pleasures (I'm not saying I'm not weird).
I do also re-read whole books when enough time has passed. I'm thinking I might be coming up on being able to re-read "A Suitable Boy" for the third time. Such a great book.
And sozlet runs out of her bagful of library books at inopportune times (like when she's sick and we can't go anywhere) and it's been so great to just dig in to our own library. I've kept a lot of books specifically for her (she just finished "A Wrinkle in Time") and she's enjoyed a lot of books that we got for ourselves (like Douglas Adams' "Last Chance to See").
A lot of the books are gifts -- it's one of the most sure-fire presents for me. The latest Jhumpa Lahiri, whatever. I have probably ten "favorite" authors at any one time and one of 'em usually has a "latest" at holiday/ birthday time.