On the flight to Brussels last night, I finished a really good book, The Making of the Fittest (2006) by Sean B. Carroll. The subtitle is "DNA and the ultimate forensic record of evolution," and he starts out with a discussion of how "DNA matching" is pretty much the gold standard for evidence in criminal cases in the United States. The ability to read and compare DNA sequences of living (and dead!) organisms is a practical benefit of years of genetic and molecular biological research. Of course that same ability has also shown us how closely related we humans are to all other life on this planet, which is not surprising considering the fact that we have evolved from earlier life forms. The ironic thing is that a majority of Americans still don't believe in this. Strange but true.
The amount of detail that is now understood about evolution at the level of DNA is amazing, and Carroll provides many examples, from color vision to antifreeze in Antarctic fish species. His explanations are detailed, talking about specific mutations, protein changes, and comparisons of nearly identical protein sequences in sometimes very distantly related animals (like blue-shifted photoreceptor proteins in eels and dolphins, a convergent adaptation to vision in deep water). This does require a little background (he provides a basic review of how DNA, RNA, proteins, etc. work), but his writing is very clear and the book is highly readable.
DNA reveals the mechanisms of the machinery of life as it works now and shows how mutations and natural selection lead to very specific adaptations. It also contains a historical record of past changes that can be used to figure out when adaptations occurred and species diverged. As the genomes of more and more species are decoded, scientists are able to expand the already detailed and unambiguous "tree of life" directly from the "code" that operates the machinery of life. Darwin would be pleased.
I would think that any intelligent and open-minded denier of evolution who is willing to read this book and follow along with these "under the hood" explanations and details would have to be convinced. But people who deny evolution are clearly not doing so on scientific grounds, and intelligence and open-mindedness are not exactly the hallmarks of religious zealots. But anyone who does want to understand in more detail how evolution by natural selection actually works should read this book.