This book is one of the most understandable and down-to-earth mathematics texts I've ever read. For instance, after presenting a new concept, he'll summarize it again in the sideline of the book every time he refers to it for the next twenty pages or so. At first, I was finding myself getting annoyed, and thinking, "What, does he think I'm stupid?"
Then I considered the alternative, the terse style of so many mathematical texts that has me regularly flipping between eight different pages trying to put everything together. I stopped complaining and started appreciating Kuipers' approach.
Kuipers does assume a certain amount of familiarity with mathematics, but not any knowledge in particular, as he reviews basic matrix multiplication and the like at the beginning of the book.
For a topic that can seem daunting (our artist always makes fun of me using seemingly gratuitous big phrases like "spherically interpolated quaternion splines") this book makes it very understandable. If you need to work with computational rotation, for a flight sim, robotics visualization, or (most importantly) for a computer game, I can't recommend this book highly enough!