I miss the days of being able to read, and to get lost in a book and finish within a day or two (or even hours!!). As a teen I used to rent 5-10 books at a time from the library and I looooved to read. LOVED IT. I find that lately I don't get into books as deeply as I used to, and I either don't have the time to read or don't set aside the time to read.
I try to keep up at Shelfari (here's my bookshelf!), but I find that I have started many books but not completely finished them.
Back to the subject... My Favorite Book. Again, this is a lot like movies for me. I read a book and may looove it but soon forget and it slips my mind. I do have one book I have read over and over.
I also loved The Nanny Diaries and Me & Emma. Those two definitely stick out in my mind though it has been a good 6+ years since I've read them.
In the past few years it seems like I've been absorbed in parenting books and self-help reading. One of my favorite parenting books is Momfulness. I love love love this. It is so inspirational and I've read it twice. I recommend it to any mom.