What a terrific book! I really like the book not only because it improves your tremolo (which it definitely does), but also because it is simply great for right hand development. The book contains tons and tons of simple exercises which are not above the complexity of a scale.
I have been struggling with tremolo on and off for quite some time -- my fingers are moving plenty fast, but it sounds like a galloping horse. I bought the book out of desperation and partially out of curiosity. The book does not come with a disk which, at a first glance, sounds like a minus (in this case, you dont need it). But let me tell you, those exercises work -- they build finger strength, independence of action and evenness when playing tremolo. After 2 weeks, I felt a difference.
Tremolo or not, doing exercises from this book will dramatically improve your right hand action. Get it! It is worth the money.