Book recommendation on recommender systems?

Recommender Systems: An Introduction by Dietmar Jannach, Markus Zanker, Alexander Felfernig, and Gerhard Friedrich seems appropriate. They also have a more comprehensive guide.

I've been reading the Recommender Systems Handbook lately, because I wanted to take part in the Million Song Dataset challenge and I knew next to nothing about this topic. It's been very helpful, although almost every chapter has different authors, and it shows. It kind of feels like a reworked collection of papers at times, but it's pretty comprehensive as far as I can tell (I've only read the chapters that I thought were relevant for me).

I wrote a 195-page monograph on the Netflix Prize and recommender systems:

"Predicting Movie ratings and recommender systems"