My boyfriend isn’t in the same field as you but has the same issues with textbooks. For him it helped to read the information before classes or any meetings so he can read it at his own pace. He would then put sticky notes next to paragraphs that only had the most important information on them. When he was in class he would just refer to those sticky notes. He says he can now skim a little bit faster because he has an idea of what important information looks like. He doesn’t need to dissect every sentence. In terms of reading for fun it isn’t necessary to read super fast as long as you’re enjoying it. However, if it really does bother you, I found that listening to the audio book as I’m reading helped me read a bit faster.
There is also the musical! It’s not a perfect adaptation (it takes some stuff influence from the 2002 adaptation) but I will always find it special because it was my first introduction to the book