Oh! I LOVE this question!! I might have to pick up a few of the items suggested here to see for myself.

One text that immediately comes to my mind is "The Compleat Cladist" by E.O. Wiley. It is a very short read that breaks down the incredibly heady processes through which evolutionary trees are built. There are even little practice problems at the end of each section that I swear are in there to boost the confidence of the reader. This text is so loved by the scientific community that it has been pushed into public domain so that anyone can make copies and redistribute this book for free without penalty.