I'm surprised how highly other people have rated this book, personally I found it slightly uneven and confusing. The author jumps from one bluff to another with little coherence or structure. He moves from limit to no limit to no limit tournaments and across the various forms of poker without recognising the differences between how these very dissimilar games should be approached and with little regard to how typical players play them.
The bluffs seem very results-oriented and some of the reasons for their success, such as the top card pairing on the river, aren't even mentioned. The author fails to understand that identifying situations where your expectation is positive is more important than having your opponent fold.
In a brief cameo interview tacked on at the end of the book, Chris Moneymaker counsels readers to bluff when a turn or river card is scary compared to the hand you think your opponent has. Basically if you want to bluff, first pick the right opponent then bet as though you have a superior hand, if you manage to pull this off regularly, don't waste your time reading this book.
People who read "How to Bluff" may come away with the idea that they can bluff their way out of any horrible situation they put themselves into. Lessinger focuses way too much on bluffs that simply will not work in real-world play, especially online. He even includes an example where a player folded pocket aces that flopped a set because the other guy in a three-handed game represented a straight that required him to have exactly JQ and to have made his hand with a gutshot draw on the turn. Would you fold a set of aces in this situation? I think not.
There are some positives. Counting your bluff outs, is a reasonable idea; knowing when your opponent is close to all-in is important, and knowing when to listen to your opponent. So some of the analysis is reasonably good. A good player who can recognise all the weaknesses may find some value.