There are many, many diagrams and photographs which help to solidify understanding, and they are all in full color. It is organized very well, although this organization has changed from edition to edition and any teacher or student using it in their courses should be aware that chapters and problems in this newer version do not always coincide with those in previous editions. The questions are excellent as well, although purchasing the solutions manual is a wise idea (it is also very well done, with long, detailed explanations of the answers to the problems).
Overall, of the 3 or 4 genetics textbooks I've looked at, this is by far the best one. In fact, it's one of the best textbooks I've ever used for any class. This one's a keeper.