I took a speed reading class years ago, and it was absurdly easy. All you do is have some kind of pointer like a pen or pencil, and as you’re reading at normal speed, follow along at the same pace with the tip of the pointer underneath the words you’re reading.
After you’ve been able to maintain that for a few minutes, start moving the pointer slightly faster, but not so fast that you can’t easily keep up. Following the pointer keeps your mind focused on reading. Do that for a few minutes, and then increase the speed of the pointer a little more. Don’t strain yourself, though. Each day I did this, I was able to go a little faster than the day before. It’s like practicing a skill. The more you do it, the faster you can go. I’ll guess I increased my reading speed 400%-500% over the course of two weeks, with no loss of comprehension.
I knew a guy who did the classic speed-reading thing where he’d spend three seconds wiggling his finger down each page. He said he could only get the gist of what was on the page if he read like that. If he wanted to understand better, he’d often have to do the finger-wiggle down the the same page multiple times.
None of this works for things like physics or calculus textbooks. There’s no easy shortcut for those.