I had never heard of quaternions so I Googled the book title you suggested. In a...

I had never heard of quaternions so I Googled the book title you suggested. In addition to the Amazon link [1], I also found a question on the gamedev SE where they talk about building a mental model of quaternions [2], which I found informative.

[1]: http://www.amazon.com/Visualizing-Quaternions-Kaufmann-Inter...

[2]: http://gamedev.stackexchange.com/questions/4801/how-can-you-...