I think he’s one of those readers who cannot take in the content of text while focusing on reading. You’ll notice he only starts freewheeling on the last word or two of a sentence or paragraph. That’s all he’s heard.

I think I first heard this from an article by Tony Schwartz who wrote The Art of the Deal. He mentioned seeing the speeches book by Trump’s bed during one of their brief meetings about Trump’s book, which Trump took no part in.