For example, I was trying to track down a copy of this long out of print book about HGL, and here's what half.com had to say about that:
If you like "The Amazing Herschell Gordon Lewis & His World of Exploitation Films" you may also enjoy:
The Divine Secrets of the Ya Ya Sisterhood - Rebecca Wells
The Red Tent- Anita Diamant
The Lord of the Rings- J. R. R. Tolkien
Bridget Jones- Helen Fielding
The Prophet - Kahlil Gibran
Unless there's some sorta crossover between chick-lit (the majority of the suggestions) and splatter films that I have yet to notice, I think these must be random, or based on popularity/sales among shoppers in general . The best I can do here is that 3 of these books were made into movies, and the book I want is about a filmmaker, ergo, half thinks it's a good suggestion.
They might as well suggest that I might also enjoy mint chip ice cream or driving barefoot; they'd have just as much likelihood of guessing right.