Number three in the genetic genealogy reading pile -- DNA & Genealogy, by Colleen Fitzpatrick and Andrew Yeiser. A couple of years newer than the Pomery book, this was published in 2005. So far, I have to say it's my favorite.
The good: Wow -- much clearer explanations of...well, almost everything! The authors start at the very beginning of what DNA is, how it is passed between generations, how it mutates, and provide very clear explanations, with diagrams and metaphors. They include sidebars to talk about genetic topics you might have been wondering about, like twins, Down syndrome and sickle cell anemia. Then they move on to what DNA testing actually tests, how to compare your results to someone else, and how to compare your results to a group of someone elses, like a surname study group; again, with specific examples and lots of diagrams and charts. To cap it all off, they even explain Bayes' Theorem and how it relates to Most Recent Common Ancestor calculations, although only probability geeks like myself will read that particular appendix.
The bad: 2005 was a long time ago, in genetic genealogy terms. This book covers Y-DNA and mtDNA very well, and autosomal DNA not at all. In addition, there are a couple of chapters that go into a lot of detail about testing companies, most of which have merged or gone out of business. It's also a little vague on the practical usefulness of mtDNA testing, although I think that may be because the practical usefulness of mtDNA testing is, well, still a little vague, so I'm not going to hold this against them.
My takeaway: Unless something better comes along, this is going to be the book I'm going to recommend at the library for people who are brand new to DNA testing, although that recommendation will come with the caveat that it omits one major type of test. I think with this book under your belt, the new book by Emily Aulicino will make a lot more sense, and will fill in the autosomal testing gap. Librarian happy dance!