I'll recommend two books: Programming Interviews Exposed: Secrets to Landing Your Next Job, 2nd Edition and Puzzles for Programmers and Pros. Especially the lat

I'll recommend two books: Programming Interviews Exposed: Secrets to Landing Your Next Job, 2nd Edition and Puzzles for Programmers and Pros. Especially the latter is a great resource to sharpen your skills on puzzle type questions. Also, there's the classic How Would You Move Mt. Fuji about puzzle questions.