This is a good explanation, with well-chosen examples, of the current state of genealogical DNA testing. I’d read the author’s Washington Post story about one of the families in the book, so I knew the solution to that mystery, but it was still an enjoyable journey. As a veteran of DNA testing (I purchased 2 of the first 100 direct to consumer tests ever sold in 1999), I was expecting to find a fair number of mistakes and misunderstandings on the part of the author, but I found only a few small things. It was also fun to revisit the history of the field and see mentions of citizen-scientist colleagues who I’ve known from conferences for years now.