The Shipping News. I haven’t read it yet, and it’ll probably have decent trade value.
We’re going to Mars, not going INSANE.
You said everyone was going. Therefore I am going. Are you saying you don’t think I’ll drive the rest of y’all mad? 
The Rubber Handbook, or similar vital reference.
Does Wikipedia come in a bound edition?
More on the theme: The Complete Science Fiction Treasury of H. G. Wells
I will bring Finnegan’s Wake, and read it out loud, at all hours of the day, over and over until we reach Mars.
Just to make everybody’s trip more interesting.
I’ll bring Gary Jennings Aztec.
I’ll bring my own copy of Finnegans Wake, to read silently, just in case BrainGlutton’s copy ends up inserted into him.
I’m trying to decide between Watership Down by Richard Adams and Lonesome Dove by Larry McMurtry. If any other Doper wants to pick one, I’ll take the other and then we’ll both be covered.
Ken Grimwood’s Replay. I never tire of rereading this book.
I’ll bring a bible. It’ll be good for posterity.
Ulysses, maybe I’d actually read it this time.
Nobody bringing any porn? That’ll be one loooooooooooooong trip 
actually I’ll bring the book that inspired my Doper name: Hašek’s Adventures of the good Soldier Švejk. Someone else please bring Catch 22!
I’m also bringing Finnegans Wake because, if it’s all I’ve got, I might actually read the thing.
I’d bring along my NY Times book of crossword puzzles. They’ll keep me entertained longer than a book will.
I’m terrible at crosswords. 
To paraphrase Hawkeye Pierce: I’ll bring a complete unabidge dictionary, because all the other books are in it.
Fiction or nonfiction? For fiction, I’m bringing Mists of Avalon, 'cause I read it every year and never get bored with it.
Nonfiction? One of (since I can’t bring 'em all) the *Foxfire*books. I figure we may need to live low on the hog for a while, and an easy reference for how to make soap or a barrel or a shotgun or how to kill and dress that Marshog might be a good idea.
A really good cookbook. There´s a reason why these sell so well.
Well if we’re all stuck on Mars, maybe To Serve Man.
We’ll be sure to toss the book out the airlock with you.
It’s not my favorite book of all time, although I am an avid fan, but either Harry Potter 3, 6, or 7. 7 is my favorite, but 6 especially have a real sentimental value to me, concerning my dad who is no longer here. The third one I remember a Valentines Day with him. The sixth one I remember having a really memorable, happy conversation with him when he had went out and got the book for me the morning it came out. 7 he drove an hour to bring to me the day it came out.