You could also listen to ebooks via a text-to-speech app. While the inflection isn't lively, you get the advantages of being able to listen to almost any book and speeding it up so it doesn't take much more time than actual reading. I've found my brain is learning to process speech faster and faster as time goes by. Of course you can speed up a normal audiobook too, but inflection and varying voices will make it more difficult.

ETA: Repligo Reader lets you tts pdf files on Android. Universal Book Reader lets you tts other formats. Google Play Books allows tts for their ebooks.