I just discovered BookSeer which is a discovery engine of sorts.
Painfully easy to use - just type in title and author and it will come up with suggestions for what to move onto next. It pulls content from Amazon and LibraryThing (though LibraryThing had thrown a moody when I was playing with this, so I wasn't getting anything back from there).
It seemed to work very well, giving about 10 recommendations from Amazon (and I presume a similar number for LibraryThing). A search for 'The Wasp Factory' by Iain Banks suggested 'The Crow Road' by the same author and also 'The Bell Jar' by Sylvia Plath. 'Here comes everybody' by Clay Shirky led to the suggestion 'Wikinomics' by Don Tapscott. 'How to use web 2.0 in your library' by, errr, me, lead to 'Library 2.0 and Beyond: Innovative Technologies and Tomorrow's User' by Nancy Courtney.
Nice resource - simple, easy and quick to use. Great to have easy to hand at the public library enquiry desk when the question is asked. However, if you don't like this you could try: