If we have to stick to novels, and I'm going to be stuck on that island a while, I want something that can be read, reread, and re-read again.
5. The Brothers Karamazov, Fyodor Dostoevsky
* Every time I open this book up, I find a new head-game. Not necessarily good for a deserted islander's sanity, but hey, still great.
4. Paradise Lost, John Milton
* Not really a novel, but close enough to count, I hope. This would be for reading aloud to the birds and the dolphins and my girlfriend, Ms. Made-Entirely-of-Coconuts.
3. David Copperfield or The Pickwick Papers, Charles Dickens
* Because I don't want everything to be gloom and damnation and epicness.
2. The Adventures of Huckleberry Finn, Mark Twain
* Not only is it great, it stands re-reading well.
1. Robinson Crusoe, Daniel Defoe
* Sometimes, you want some escapist entertainment to distract you from your struggle for survival.
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My favorite novel of all time is tough to pin down, but it's either David Copperfield, The Master and Margarita, or Terry Pratchett's Mort - the last being one that I wouldn't re-read, for fear of destroying the nostalgia value.