I'm a former competitive swimmer and now enjoy swimming for a good workout and to train for triathlons. This book is great for former swimmers because it has longer/harder workouts, makes good use of sets, and has sections for distance, mid-distance, sprint, IM, and stroke.
I'd say it's not quite fit for a beginner swimmer because the workouts tend to be longer and it doesn't really teach you good swimming technique.
It makes good use of different training methods (negative split, sprint/recovery, kicking, pulling, building, descending, etc) and gives you a specific thing to work on with each workout.
Another nice thing is that each workout has an A and B option. One option is longer and the other is shorter.
Overall, I'm really happy with this book. Previously I would typically write my own workouts since most swimming books I found were more geared toward beginner or non-competitive swimmers. This book is a good fit for me and a great transition out from competitive swimming for 15 years.