The book's title might cause you to be disappointed if you're looking for a complete resource on slot machines. There is a chapter devoted to them, but this book is not a half slot machines, half coin-op guide as the title suggests. My guess would be that slot machine collecting was at a peak when this book came out and the book was titled to grab attention.
A more appropriate title might have been "History of Coin-Op Games including Slot Machines".
Besides that, if you want a mini-history of these machines along with some nice color pictures, this book is for you. Time period covered is 1889 to 1988.
There are 9 chapters covering Penny Arcade Machines, Baseball Machines, Gun Games, Bowling Machines, Pinball Machines, One-Armed Bandits, Novelty Arcade Games (part 1), Novelty Arcade Games (part 2) and Owning Your Own.., along with an author's introduction and an index which directs you to every page a particular game is mentioned or a picture is located.
Well written book with lots of pictures to remind you of times past and games you have long forgotten about. If you're over thirty, you will have many "oh, I remember playing THAT one" moments.
You'll be glad you added this one to your game-room collection.