Introduction to Recommender Systems Handbook
Francesco Ricci, Lior Rokach and Bracha Shapira

Recommender Systems (RSs) are software tools and techniques providing suggestions for items to be of use to a user. In this introductory chapter we briefly discuss basic RS ideas and concepts. Our main goal is to delineate, in a coherent and structured way, the chapters included in this handbook and to help the reader navigate the extremely rich and detailed content that the handbook offers.

http://www.inf.unibz.it/~ricci/papers/intro-rec-sys-handbook.pdf