Router Magic by Bill Hylton

I include this book at the top of my list because it really took my router work to the next level. Although printed in 1999, the information remains relevant today. Bill explains how routers and their bits work, and covers a huge range of useful specialty bases for the router.

The book is out of print, but can be found used on Amazon. If you ever see one in a book store, at a yard sale or whatever, buy it.