This got my interest and given the readers we have on this site I think you'll peruse it as well: http://www.booklamp.org/ .

"BookLamp.org is the result of an exploratory project intended to help you find new books by comparing the content of the books themselves, similar to the way that Pandora.com matches music lovers to new music. We're attempting to help you find books with similar themes and writing style to books you've enjoyed in the past - comparing elements like Description, Pacing, Density, Perspective, and Dialog - while at the same time allowing you to specify details like... more Medieval Weapons."

Biggest problem right now: not enough books in its database.

Yes, an interesting idea but still needs work. Obviously, you are right that the data base is inadequate since the only Heinlein work it includes is Red Planet. RP produced a lot of Philip K. Dick works as recommendations, which doesn't work for me.

There are a number of Asimov's books in the database so I tried a few of those. Foundation produced more P.K. Dick and Star Wars. I guess there are comparisons that can be made between Foundation and Star Wars in that they both are big stories about galactic empires with secretive societies playing key roles. I must admit I hadn't considered that before.

I like the idea of Booklamp and hope it grows.