It is absolutely worth it. I’m just started to reading them, and they seem to be helpful, but I have’t practiced yet. At least read the first one, really good advices are on it by people who stuttered themselves. Also [check this](https://reddit.com/r/Stutter/comments/n1gk4t/anyone_in_here_knows_joseph_sheehan_hes_known_to/) I posted a while ago. Joseph Sheehan considered to be one of the most successful speech therapist of hi time.