I've had trouble with reading books or really anything longer than a slatestarcodex post- I just start skimming, and then I have to backtrack because I didn't really read parts at all, and then I get bored and/or frustrated and quit. So if you have that problem too I found something that might help:

This text to speech app takes a pdf file, breaks up the text, and then highlights and reads individual lines. I think the key is engaging more than 1 sense. It's less effort than reading normally because of the voice, the bite sized chunks, and the fact that it's not really possible to lose my place. And I seem to listen more actively when I follow along than with audio alone. Also, critically, the playback speed is adjustable. This wouldn't work for me if I couldn't speed up the voice to more closely match my reading speed.

The default robotic voice is a bit off putting- the best free TTS engine I've come across is called IVONA, though it doesn't seem to have male english voices. Also I've found that adding some sort of quiet ambient or classical-like music in the background can make this more pleasant.