If you consider the fact that one third of your life will be spent sleeping--that is, if you live to be 90 you will have spent 30 years in a coma-like state--it might seem that those years could be spent more "productively". Some of the touted benefits of lucid dreaming include: gaining spiritual insight; being able to work through past traumas; solving problems, be they mathematical, scientific, or philosophical; improving creativity; and being able to experience conditions that are otherwise unavailable (for example, a woman confined to a wheelchair could "fly" in her lucid dreams, enjoying freedom from the terrible weight of gravity that governs her waking state). All this is well and good. But I don't really see how it is so very different from concentrated meditation, or participating in a session of active imagination, except that it is more challenging. Given that your body is in a state of atonia (REM stage of sleep muscular paralysis), lucid dreaming requires some degree of training and discipline.
No problem, according to Wallace. He believes that we all can dream lucidly and provides instructions in relaxation and dream journaling that will help toward that goal. I came to this book more out of curiosity about sleep and dreams in general, rather than specifically to learn how to lucid dream, so I am perhaps not the target reader, and I remain somewhat skeptical. Nevertheless, I found the book to be intelligently written, and the uncomplicated techniques appear to be well designed to achieve the goal of lucidity in dreams, if that's your aim.
To my thinking, the real feat would be to "wake up" from the dream of consensus reality. The second part of the book, on Dream Yoga, addresses this, but not as extensively as I had hoped. Dream Yoga is a specific spiritual practice, as opposed to the secular techniques that Wallace offers in the first part of the book. In speaking of Dream Yoga, Wallace seems knowledgeable and he makes a good point--if we can attain lucidity in dream it is excellent practice for the next step, that of attaining enough clarity and stability in our waking life to come in contact with our "primordial consciousness", our Buddha nature. What Wallace is offering in this book are techniques for learning how to be "present in the moment"--both in dream and in waking. Having only read his proposed techniques, I have no personal experience that acting on them would be helpful; but the process sounds feasible enough.