I've never played D&D (or any tabletop RPG), but I'm aware of its massive influence in computer gaming, fantasy fiction and other areas of modern popular culture. On beginning the book, I was relieved that the introduction explained this is intended as an introduction, rather than an exhaustive history of D&D.
Unfortunately, the book is written in a very chatty style, with many pointless asides, and hints but never gels into a history of tabletop roleplaying games, the Dungeons & Dragons franchise, or Tactical Studies Rules/TSR Hobbies. This last one in particular needs a rather better book all for itself; what little there is about Gary Gygax's maneuvering to remove his partners and being removed by Lorraine Williams in turn, and the company being nearly driven into the ground before being bought out by Wizards of the Coast (in turn bought out by Hasbro) would make some fantastically entertaining reading.
Reached the end, almost gave it two stars, and decided to read the notes. I'm very glad I did - they directed me to www.ofdiceandmen.com to read more about the Lorraine Williams and Wizards of the Coast years, which are very sparsely covered in the book.