I totally agree with Mrs M's post that a favorite book, just like a song, can depend ALOT on where you were in life when you read it. some things resonate with you at 30 that maybe you couldn't relate to at 20. I too have an entire shelve of FAVORITE books--these are the ones I never pass on, never lend out, etc. I also hve to say there are so many different genres of writing out there, I'd probably have a FAVORITE for almost every type, and for sad and for funny, etc.
that being said, I LOVE the outlander series by Diana Gabaldon. I started reading it whn i was about 21 yrs old and it was the book that made me want to go to Scotland, which I DID. I lived there for an entire year and it was FANTASTIC. The chance to explore another country, to meet new people, to study history in the place where the history WAS made, on and on. I hope if I have children some day, THEY too take the chance for overseas study/travel.
For animal related, my favorite book right now is Marley and Me or Beautiful Jim Key. However, that could change at any time since i read SO MANY great animal-related stories.
Anyway, the point being is how can I decide on JUST ONE???