Some books entertain, some inform; some confirm what you already knew, some make you change your mind about something. But then there are some books that just make you think "wow! I wish I'd written that".
For me, Charles Petzold's The Annotated Turing falls into that last category. It's a book worth reading not only for the topic itself but the way it's presented.
He provides the necessary background before working through Turing's famous 1936 paper "On computable numbers, with an application to the Entscheidungsproblem" with rich annotations at every stage, including biographical details.
If you are interested in the foundations of mathematics, computability, Turing's work, or even just ways of explaining mathematics in a historical context, I highly recommend this book.
The original post was in the categories: mathematics books but I'm still in the process of migrating categories over.