[Self-Therapy for the Stutterer](https://www.stutteringhelp.org/Portals/English/Book_0012_tenth_ed.pdf) really helped me. It's motivational, but not in a self-help bullshit kind of way. There's some really cool exercises and technical stuff that helps. I consider my stutter under control nowadays, mostly due to speech therapy along with the stuff I got from this book. Then there's also [Redefining Stuttering](https://www.mnsu.edu/comdis/kuster/Infostuttering/Harrison/redefining-stuttering.pdf), which I actually never got around to reading in its entirety because I only found out about it later on during my therapy. It's pretty big, but also a great book with tremendous insights. The links above have the full books in .pdf. The books are available for free too, so it's not illegal. I hope they help you.