I suppose the way you tell is the books you've read loads of times? Then mine must be Lord of the Rings too. I keep having children just so I can have an excuse to read it aloud again (along with the Chronicles of Narnia, The Once and Future King - makes me cry, that one - and lately the His Dark Materials trilogy). I loved the films though. Peter Jackson and I must have similar imaginations.
Other books I've read several times are Rebecca and Wuthering Heights. I also love Tristram Shandy, but that's a bit of an acquired taste.
I'm dying to read some Elaine Morgan at the moment who's written some controversial books on human evolution, but my local library doesn't stock them.
If they aren't on eBay I'm going to have to actually pay full price.
