My only real critique of academic books, was that the exercises varied A LOT in difficulty. Some books had exercises that seemed to assume that the reader had been a honors student, and thus able to pre-process/setting up the problem with intricate identities and what not, before coming to the part where you apply some theorem. Now - no big problem if you worked with very keen math students, and they'd show you that,…
All of this to say, is it's really necessary to have guidance with it, and to make sure you actually do problems, not just convince yourself that you know the material.