Long story short: If you are looking for a *very basic* introduction to (non-realtime) computer graphics with a "focus" on photon mapping, this ain't a bad deal. I'd recommend getting it used though.
On to review:
The book has a few typos, but only two or three that really caught my attention. What I found worse however, is the author tends to restate something in two consecutive sentences - or write a long, convoluted sentence where even I could come up with something short and clear. This was annoying, but sufferable. Overall this book could have used a more attentive, hands-on editor... perhaps another day.
That aside, the book provides an practical introduction to photon mapping from the basic level - that is, he covers it's raytracing foundation, super-basic electromagnetic theory, basic scene-graph management, and some similar topics. He then covers the basics of photon mapping itself - what photons are, and how you use them to generate images. This is more of a "practices" book than a "principles" book though, which is good for folks like me who barely remember attending high-school calculus.
Again, these things are great for people who don't know much about computer graphics, but perhaps not so much for those already in-the-know. Sorry guys, but you've already got text by Mr. Jensen himself. :-)
That said, the book certainly leaves a lot for you to discover like others have discussed. You won't be competing with Mental Ray, Brazil or Photorealistic Renderman with just this book. :-)
Given that it doesn't have much depth on the subject and the fact it spends so much time on the basics, I'd have to recommend this only to people with little experience with computer graphics and then probably as a used purchase.
I give it three stars because despite it's problems, I actually did learn a bit from it.