Jacob and Patricia Cohen wrote "Applied Multiple Regression/Correlation Analysis for the Behavioral Sciences," which went through two editions. Leona Aiken and Steve West wrote "Multiple Regression: Testing and Interpreting Interactions." Each of these books were wonderful on their own. When I found out that a third edition of "Applied Multiple Regression/Correlation Analysis for the Behavioral Sciences" was coming out, I was surprised, as Jacob Cohen had died a few years back. However, with Leona Aiken and Steve West on board, I knew that the text would be great, and pre-ordered it. I always tell my intro grad stats class that if they have some money burning a hole in their pocket, they should spend it on Cohen, Cohen, West, and Aiken. It does wonders talking about interaction and advanced topics such as generalized linear models and multilevel models. The reason I only give it four stars is because there are parts of Aiken and West's book that are absent from the final copy (and as of yet not obsolete), so the fact that it doesn't do everything that the past two books did makes me wish for slightly more from it. However, it still does much of those two as well as much more. I would recommend it as required reading for anyone who hopes to do psychology research.