Definitely, The Lord of the Rings. Such good literature on so many levels. I know Tolkien said it wasn't allegorical, but there's always something new to find.
Gates of Fire by Stephen Pressfield. Probably the best study on leadership I have found. And I think he is correct in saying that the opposite of fear is not "fearlessness", but love.
Cryptomonicon by Neal Stephenson. A great adventure, wonderfully sardonic pose, and absolutely hilarious.
Interesting Times by Terry Pratchett. My favorite Discworld novel.
Yes, eclectic and idiosyncratic. But there they are.
To die for an idea; it is unquestionably noble. But how much nobler it would be if men died for ideas that were true?- H.L. Mencken