Many bridge books only illustrate technique by means of one example hand, and another, and another: "Here's a hand. Here's how to do bid (or play) this hand. On to the next hand." The refreshing thing about Mr. Klinger's books is that he starts with a principle, explains it in depth, and then gives an example or two. This way, one learns not to play just the hand in the example (which one will never encounter in real life, anyway), but all hands of a certain type.
If you read nothing else, you will find the first chapter on the "Rule of 21 & 1/2" worth the entire price of the book. This improves greatly on the old Rule of 20 for deciding whether to open with a 1-bid, to preempt, or to pass. Example: the Rule of 20 will tell you to open this hand: QJxx Kx QJxx QJx -- 12 HCP and 8 cards in the 2 longest suits, right? Wrong.
Experts probably use an algorithm like this, whether from this book explicitly or just through their experience and judgment. You can see this by observing some of their openings on Bridge Base Online's Vugraph sessions. Intermediate players can now make their opening decisions more like experts, using the simple formula Mr. Klinger gives.
This method of deciding when and how to open has helped me reach slams, games, and solid part scores that others did not reach. Opening also inhibits the opponents' bidding.
There's good advice throughout the rest of the book, too. This is the second book I've read by this author and both have helped me greatly.