I should start this review with an honest disclosure: I, like the real Lovecraft, am a committed materialist. Donald Tyson is anything but a materialist. Despite my materialism, I am generally a curious and open-minded person, and I spend a good deal of time considering alternative views on the universe. This book is not my first exposure to Tyson. In fact, I have read many of Tyson's books with more than a little interest, however I have never found any reason to believe that Donald is correct in his endorsement of a "magical" universe.
Most of Tyson's recent works have been on Lovecraft and trying to turn his mythos into a workable system of ritual magic. I applaud Donald's creativity, and admit that he can even tell a pretty engrossing yarn at times, (See his book "Alhazred" for a good, if at times disturbing, read.) but I am certain that Lovecraft himself would be horrified to find his works of fiction being used to support anything founded in the occult.
From a strictly biographical point of view, this book is pretty well put together. Donald takes an interest in his subject that inclines him toward a good amount of detail, which is excellent. Often times Lovecraft has been painted in brush strokes that are so bold as to completely obscure his regular, everyday humanity. On the downside, Donald cannot help but impose his own magical point of view on Lovecraft, and although he repeatedly points out how Lovecraft would never approve of seeing himself as having anything to do with the occult, the undertone of the book is that Lovecraft was just somehow struggling with the deeper, darker truth of his dream-born occult powers. I take issue with interpreting Lovecraft in this way for various reasons, most importantly because Lovecraft did not see himself this way. Although deep internal struggles and denial make for great fiction, most of us, Lovecraft included, don't live in total ignorance of our own natures. Lovecraft, being a deeply intelligent and insightful man, was no stranger to analyzing himself, and I fully believe that he had a pretty good handle on his own nature.
All in all, I would suggest this biography to others, but I would include a warning to carefully considered every time Tyson inserts his own opinion. Take commentary with a grain of salt, and you'll learn quite a lot you probably never knew about Lovecraft.