The first reviewer says skip this and go to Thomas Cleary. I would assume that means "Entry into the Inconceivable". I have both actually, and I like "The Buddhist Teaching of Totality" better.
To me, the Cleary approach seems to be just to pick you up and dump you right into the middle of things. By page 24, you're already into the four dharmadatu's. These are very subtle concepts that require serious preparation to understand deeply. They may be interesting doctrines if you're into that kind of thing, but I personally like to see how all the pieces fit together. In that sense, I'm totally lost. The Garma Chang book covers a lot more basics before going into the heavy stuff. The pace may be slower, but in the end, I have a much clearer picture. And after that, the Cleary book becomes much more palatable.
Another reviewer mentioned that Garma Chang seems to think he knows everything. I don't know, but from the writing, it's clear that he has a great deal of personal experience on the subject at hand. His discussion on emptyness, for example, is particularly subtle and insightful. Thomas Cleary, on the other hand, doesn't seem to show much opinion of his own. Much of the "Entry into the Inconceivable" text is translated from Chinese works. Same goes for his translation of the Avatamsaka Sutra itself as well. Even the introduction is paraphrasing of Chinese text. Not that translation is not useful of course...
A bonus included in the Garma Chang book is an almost complete translation of "The Great Vows of Samantabhadra". It is important because it's supposed to give one a good feel for what the complete Avatamsaka is like. It is the last part of the Forty Hwa Yen and is often treated as a separate sutra on its own. (It's also classified as one of the Five Sutras of Pure Land) And it's not in Cleary's English translation of Avatamsaka Sutra, which is strictly a translation of Eighty Hwa Yen.
In any case, I'd probably get both books. They serve different purposes. Seems to me that the person who says to skip this one is treating the meaning of the books as self-existent and real and therefore their relative merit should be completely self-evident. We all know that is not true right?
The Hwa Yen school, which drew chiefly from the Avatamsaka Sutra (translated by Cleary), emphasizes Dharma from the perspective of realization, or enlightened mind. Like the Lotus Sutra, The Avatamsaka Sutra is equally an evocation of a state of mind as a presentation of information. The Hwa Yen thinkers of Sung China used this as their starting point to paint a dazzling portrait of our universe filled with mind-blowing images and rich ideas.
This is a pretty good introduction to Hwa Yen Buddhism, although the reader will have to wade through a fair amount of unapologetic sectarianism. Hwa Yen, we learn, is the "highest" and "most advanced" form of Buddhism, and Chang clearly considers himself to have full knowledge of what Buddha "really meant" in his teachings. Despite this sometimes tedious lack of modesty, the book is a good overview of the history and doctrine of this school. Given the unfortunate paucity of material on this intriguing movement, that is a welcome addition.