This is an excellent book. But it is not primarily a guide for clarinetists who want general advice on subjects such as embouchure and reed selection. Jack Brymer's book, "Clarinet," is a guide for clarinetists. This is a book about the clarinet that anyone interested in the clarinet can appreciate. Still, it does include some expert advice on plenty of topics, including embouchure, tone, fingering, synchronization, and so forth.
This is more of a survey of all the different clarinets (as well as their histories), clarinet repertoire, and modern trends. There are nice chapters on the clarinet family, including the high clarinets, the C clarinet, the basset horn, and the bass clarinet. The basset horn is famous for its huge range (four octaves!). But Georgina Dobree explains that it isn't easy to play. You need a soft reed, you have to be careful in all registers. And although it is easy to hit the high notes (especially if you have one of the smaller-bore ones), you may need alternate fingerings to play them in tune. Personally, I think the basset clarinet is a better instrument to learn, if you have the money to acquire one.
Michael Harris discusses my favorite of the clarinets, the bass clarinet. I like it because its range extends far enough down so that one can play a wide variety of parts. Harris again explains that it isn't so tough to hit the highest notes on this instrument, but one has to choose a mouthpiece that lets you hit the next highest octave as well. Roger Heaton's chapter includes some good fingering choices for the highest notes.
Then there are chapters on the clarinet repertoire, players and composers, clarinet recordings, the clarinet in jazz, the mechanics of playing the clarinet, and teaching the clarinet. Then we get some expert advice on how to play historical clarinets, from Colin Lawson. It's written in a style that is interesting for us non-professionals. Next is some explicit advice for the prospective professional clarinetist, from Nicholas Cox.
The most fascinating chapter is by Roger Heaton, on the contemporary clarinet. That covers some topics such as high note fingerings, microtones, and circular breathing.
You don't need to know much about the clarinet to enjoy this book. But to profit from the more expert advice, you need to play the clarinet fairly well already.