I haven't read the book, I have read reviews and been listening to his podcast.

It seems that he likes SBF on a personal level, which I think is reasonable, but then it seems that he falls short of making strong statements about the fraud. I think people have interpreted this combination as an implicit support of SBF, where it could in fact just be that, publishing before the trial, Lewis didn't want to "call it" the wrong way and limit the relevance of his book.