As a former student of Mr. Miller, I can hardly claim not to have some sort of bias. However, I have yet to encounter a book on vocal technique that is more insightful or more complete. Mr. Miller is one of a number of pioneers who promote the idea that good vocal technique is based on physiology and basic scientific principles (imagine that!). He is a no-nonsense get-down-to-the facts kind of guy when he writes about vocal technique - a welcome contrast to some other works on the subject.
TSOS covers all the major topics in vocal technique in considerable detail - be prepared to look at diagrams and learn terminology. But most of all, be prepared to _understand_. If you find the amount of detail daunting, not to worry - TSOS is well divided into sections, so you can get away with jumping around without too much trouble.
Always entertaining to read and with an unmistakeable style, Miller does not shy away from criticizing certain popular ideas. But more than just criticize, he explains _why_ certain notions are wrong, and what you can do to avoid common pitfalls.
An absolute must-read for the modern singer. Enjoy!