I do not offer this review as some form of counter-argument against the other high rated reviews about this book, but only to compare it with Hagen's better work.
Whilst there are some good chapters in this book, I would say that it is a fairly softly delivered and fragmented piece of work. It has an important difference from the earlier best-seller, Buddhism Plain and Simple (BP&S): The latter is a structured presentation of the main teachings of the Buddha, and so one can expect to start at chapter one and read through in a progressive way. In "Buddhism Is Not What You Think" one finds what amounts to a series of short essays. In fact this is indicated in the copyright and publishing data at the beginning of the book, where one will see that the book is really a compilation of talks and articles delivered by the author at the Dharma Centre in the USA. It has been shuffled together in what the author no doubt thought was a themed way, but I don't think it quite works.
The advantage of the unstructured characteristic of the book is that one can pick it up and read at random, without missing out a vital earlier element of the Buddha's teaching. The disadvantage, for me, is that the author doesn't really engage with the reader for long enough, on any particular topic, to shift his/her consciousness into a radically different perspective. Even if one reads two or more chapters in one sitting it is no different, because the topics being addressed do not flow naturally into each other.
Overall I would recommend it - as a gentle read and prompt for reflection - but it all comes across as rather safe and uncontroversial; unlike BP&S which, with the exception of two chapters I found profound and mind-altering.