This is a great book for the beginning kayaker. I have canoed and sailed for close to 40 years and just recently took up kayaking. After several lessons and going out on my own a few times I bought this book. It filled in a lot of the blanks and is a very balanced presentation of the subject matter.
The kayaking instructor that I went to is definitely a knowledgeable individual but he is, as I have found many in the sport to be, very opinionated. Had I not read The Complete Sea Kayaker's Handbook I think my knowledge of the sport would have been limited to what I learned by trial and error on my own and the limited presentation I got from the instructor. The book is pretty neutral on subjects that are more personal preference like boat selection, skegs vs. rudders vs. neither, paddle selection, etc. There is good coverage of the safety aspects and equipment, beyond what was in the lessons I took.
Overall the book is a really good supplement to lessons and paddling experience. I find myself going back and rereading sections of it after each time I go out paddling. I am sure that will change with experience but it is a great reference.