It is instructional as well as a transcription book, the balance tends to go to transcription however. Although some comments about scales and techniques are present, most space in the book is dedicated to the actual transcriptions.
I find playing hendrix songs in general is good for improving playing skills (but hard!), but with my metal background I have quite a lot of difficulty with his timing.
For this reason, the added value is definately in the included cd, which not only sounds as a very good approximation of hendrix himself, but is recorded in a very transparent way, and with some solos on slow speed, which makes it much easier to learn hendrix by ear.