Excellent. Back in the day, it helped me break the Expert barrier. There's a big difference between playing reasonable chess each move, and playing chess with well thought-out plan which binds the moves together.
By the way, this is a book that it is critical that you put immense effort into it. Do the exercises. Work really hard on each one, take as long as you require. There are lessons to be learned by players of many levels, but this book is especially helpful for learning how to evaluate a position and then form a plan based on that position.
The Winning Chess Series that is credited to Seirawan and Silman has a pretty good tactics primer (Winning Chess Tactics). For what it's worth, I read an interview online with Silman where he stated that he "wrote most of that stuff." Sorry, I don't have a link to the inerview, so unless anyone can verify it you'll have to just take my word for it (or not).
Brian
EDIT-I think the best tactics book is 'The Ultimate Chess Puzzle Book' by John Emms, as it has brief explanations of the motifs in the beginning, then tons of puzzles to grind through arranged by difficulty, with no hint as to the tactic used.
