Everyone's talking about The Turn of the Screw, but there was another book featured in the episode Orientation that is much more important, which one of the writers even confirms. This book is called The Third Policeman, by Flann O'Brien. We see it for about a second when Desmond is gathering his things.
Lost writer Craig Wright said in an article "Whoever goes out and buys the book will have a lot more ammunition in their back pocket as they theorize about the show. They will have a lot more to speculate about -- and, no small thing, they will have read a really great book."
Here's a link to the full article on the book and Lost, but beware if you're interested in reading it, the article contains a spoiler to the book.
http://www.indystar.com/apps/pbcs.dll/arti.../509290361/1007
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