If you've read the other reviews on this page you'll see a pattern emerging: those readers who don't come from Edinburgh found the book entertaining, but those who do found it disappointing, and I must add my name to the latter category.
As a lifelong Edinburgh resident I've heard stories of the underground city all my life, and the emergence of this book offered the promise of a full and final explanation of what's really there and what isn't. However, aside from a reasonably interesting general history of old Edinburgh, the book is astonishingly lacking in facts of any kind. It's all conjecture, rumour and myth. At least fifty percent of the book is merely a series of fables and ghost stories with absolutely no descernable facts or evidence to either back them up or dismiss them.
If someone's going to bother writing a book on the underground city, wouldn't you expect them to have something to TELL? Not so Jan-Andrew Henderson. For him the gathering together of a few myths and legends was enough. No solid research, maps, plans or diagrams, descriptions of exactly what remains of the underground city; No reports of excavations, eyewitness accounts; no rummaging through old property plans or title deeds to discover reports of mysterious doorways in lost cellars that seem to lead nowhere. None of this.
If you're really interested in learning about the underground city you'd be better off saving your money, and instead paying a visit to one of Edinburgh's many pubs in the old town, where you'll encounter characters who can tell you much more about it than anything in this book.