I find some of Baker's works brilliant and others terrible. His "How To Play Bebop" series fits in the brilliant category and you really should get all three. Volume 1 is the most essential of the series, then volume 3, and lastly volume 2.
Baker is usually credited with inventing the term "bebop scale". In volume 1 of the series he describes the bebop dominant and major scales scales are and also gives you some rules for using the scales to construct bebop lines. Some of this is quite technical and may put some readers off, but if you play through the examples and use your ears you will soon catch on.
The basic idea is to add chromatic passing notes in the right places so that the your lines contain chord tones on strong beats.
He also shows techniqes for extending and connecting bop lines and provides some of his famous perpetual motion exercises to work on. There's a lot to keep you busy in this book.
It is often difficult for the beginning jazz student to know how to go from scales to improvisation. This book gives you something concrete to work with. It is a bit bewildering at first, but if you give it time to sink in you will find that you will be able to internalize the many rules and create long and sophisticated improvised bop lines. (Note this book is aimed at creating single-note lines only and does not cover chord voicings or comping).
A slightly more modern treatment of this subject can be found in volume 3 of Bergonzi's opus
Inside Improvisation, but I prefer Baker's book - it's the original and best.
Volume 2 of the "How To Play Bebop" series is a compilation of patterns to play over particular chord progressions (ii-V-I, turnarounds etc). As such this book is purely for vocabulary once you already have gained a grounding in the structure of the bebop language from volume 1.
I find the best way to approach this book is to play through a few of the patterns until you find one that appeals to your ears and then work it out in all keys around the cycle. You can also try modifying it to fit other types of chords by raising or lowering a third or fifth etc. where appropriate. It's also good to connect a few patterns and create a line that runs over the changes of an entire tune.
This book has little in the way of text and is essentially just musical examples. It is up to you to work out the best way to use it. In the context of the series it is a very useful book, but it's probably not quite so good to have in isolation. It's still well worth having though and the patterns themselves are very tasty.
Volume 3 is about how to learn and internalise tunes. This is a book that is useful in a broader sense than just the bebop genre. He covers techniques such as creating guide tone lines, playing chord tones, learning contrafacts, and more.
With the steps written out in detail for several examples, he explains the steps you should go through to learn a new tune. By learning and internalising the tune he means really knowing the melody and chord changes intimately and being able to improvise over it fluently. You can save a lot of effort by realising that many jazz tunes are contrafacts or partial contrafacts and Baker gives many examples of these. A contrafact is a tune with a different melody but the same chord changes. For example there are many, many songs based on the blues form, and nearly as many based on the changes to "I've Got Rhythm". There are many others. For example the tune "Ornithology" is based on the changes from "How High The Moon", "Groovin High" is based on the changes from "Whispering" and "Hot House" is based on the changes from "What Is This Thing Called Love?". Other changes are partial contrafacts which might contain sections with shared changes (e.g. "Take The A Train" and "The Girl From Ipanema").
This is an excellent series for anyone who wants to play jazz.
http://rapidshare.com/files/259601503/David_Baker_How_To_Learn_Be_Bop_1-2-3.rar
