I own all of the "Graphics Gems" Series. This one is probably the best. It really truly is a classic. I'll get to the reason for only 4 out of 5 stars in a moment.
As the description says, it's a collection of articles that cover solutions related to geometric problems and graphics techniques. It is wonderful for browsing and becoming exposed to little tricks and tips, or just seing the types of problems that people have solved that you never even knew existed. The way I learned to appreciate this book was browsing through it in a bookstore. I didn't have the money at the time to buy it (in college). Later, at work, I needed to solve a geometric problem, and I remembered that this book has an article on the problem I was solving. I went out and bought it, and have since refered to it on many occasions, including writing my own geometry-related book, "3D Math Primer for Graphics and Games Development."
My four-star rating is based on a buyer in today's market. As I mentioned, I own the entire series and have worn the pages to bits. At the time it was first published, I would have given it 5 stars without a doubt. However, some of the material is related to problems that are not important problems for many programmers anymore, such as software rasterization. At the time, some of the material was very new and this book was one of the few places to find it. However, since then, most of it has been well covered in more up-to-date graphics or "geometry toolbox" books that offer better diagrams and clearer explanations. Also, the sample code is old-school style C code and a bit messy in my opinion. It's probably not a good book for learning, either.
In summary, this book, like any "Gem" book, is great for browsing and becoming exposed to concepts. However, for today's buyer, I think there are better alternatives that should be purchased before this book. Real-Time Rendering is a good survey of graphics techniques. Eberly has written some good books for geometry toolbox. For learning, I'd recommend my book of course! But this still is a great classic and many experienced programmers have it on their shelf.