You're stuck on a desert island for an unknown period of time.

The Ultimate Hitchhikers Guide (Douglas Adams) -- like Shannon, I will cheat and take the single volume version.  Unlike the traitorous Shannon V, I will make sure that I put this most important work first on my list.

1984 (George Orwell) -- just in case it's not a real island but a conspiracy of Big Brother.

Siddhartha (Herman Hesse) -- journeys of self discovery are always handy when you're the only person to discover.

Collected Poems (Philip Larkin) -- for scathing commentary on the people and society I'm not likely to ever see again.

The Rubaiyyat (Omar Khayyam) -- just because it's awesome.  And beautiful.  And handy if I find an oasis populated by goatherders.

The Great Gatsby (F. Scott Fitzgerald) -- to remind myself that people who disappear without explanation for many years can come back and be successful... And to prove that although it's possible to live without alcohol, it's very dangerous.

The Lord of the Rings (J RRRRRRR Tolkien) -- I might even read all the appendices.

That's all I can think of without making stuff up... though I've liked plenty of other books I certainly wouldn't want to have them as the only thing to read for the rest of my life.  And I'm so not taking Robinson Crusoe.

Also, may I recommend self-cannibalism.  To paraphrase Brillat-Savarin, "you eat what you are".