I realize that in any spiritual teaching, certain concepts are going to be repeated. This is necessary, especially since the concepts presented are probably going to seem new to most readers. However, I felt that the whole book was nothing but a repetition of this general idea: the mind is the root of all problems, because it has taken us over (meaning that we can't control it, but rather, it controls us). However, we can free ourselves from this by becoming totally present.
The author then elaborates on this statement using many different phrases, such as, "Feel the power of this moment and the fullness of Being. Feel your presence" (pg. 70). He also uses the typically vague promises that tend to accompany books like this, such as, "...You can be at peace. There may be sadness and tears, but provided you have relinquished resistance, underneath the sadness you will feel a deep serenity, a stillness, a sacred presence" (pg. 148). To me, it seemed as if the author was simply repeating the same basic idea over and over again; which, again, is not necessarily a bad thing. However, it begins to become annoying when the book has as many pages as this does; and after reading all of them you feel as though you could have just read the title and received all the information from that.
As I said previously, the idea of this book was very promising. Even the techniques contained within the book, though inspiring, were never very well explained. After reading this book a couple times, I still don't really know how to get to that spot of inner peace. I don't know, either, how to feel the "...still, observing presence itself behind the content of your mind, the silent watcher" (pg. 46). I don't even think there was a technique telling you how to achieve that, actually. Sure, the author has included some meditations, but they're nothing new. The same old "Direct your attention into the body. Feel it from within" (pg. 93) type meditations, which can be found almost anywhere else, even on web pages (for free, no less) are included in this book.
Overall, this book did not live up to it's hype. I found it to be long and rambling; the author took the title of the book and expanded it into 191 pages full of the same idea phrased with different words. He attempts to tackle some other subjects too, of course, such as relationships. However, he basically uses the same "power of NOW" approach to these as well; meaning that he suggested a relationship would evolve into true love when both partners had eliminated their respective egos and become completely immersed in the now. That's the solution for EVERY problem, it seems. So he's just using the same message for different problems, which seems to be more of a "pie in the sky" promise to me.
The central theme of this book is spending more time in the "Now"; but there's clearly such broad agreement on this that it seems odd to dedicate a whole book to it. The best way to experience the Now is to practice a daily meditation routine, though there's very little guidance within Tolle's book. There are many good books on meditation and you would be far better following one of these than getting too hung up on Tolle's philosophies. (p.s. my personal favourite for real-life meditation is Eric Harrison's "Teach Yourself to Meditate").