Jelte Rep's Great Mahjong Book, originally published in Dutch, is an interesting tour of mahjong around the world. It starts from the history of the game - not thousands years like many sources like to claim, but actually more like 150 years.
Then he takes a look at how the game is played in the US, Japan, China, other Asian countries and several European countries. The local variations are described, not always in great detail, but detailed enough so you can try them out if you wish. If you want to learn a particular style well, get a book or a web site focused on that variant, but for a general overview, Rep's book is excellent.
Add to that a sleek, stylish layout and plenty of good pictures, and you get a rather fine book on a rather fine game. This book will serve both newbies and enthusiasts.