It’s my understanding that those sorts of classes, speed-reading and such gimmicks, are rubbish. The only way to improve reading skills is with practice. If you’re having issues with absorbtion or comprehension you might see about reading with a pencil in hand to underline key points. You’re less likely to glaze over if as you go you’re consciously evaluating and picking out what matters most. I like to make notes in the margins as well. Writing out my thoughts, even in just a few words, helps clarify things for me.