After the book is written and polished, read it aloud to a friend
Writing advice from Neil Strauss:
This is the key piece of writing a book for me. When I’m all done with a book, I’ll call a friend or have a friend come over, and I’ll read them the entire book from front to back. And they don’t even need to respond — I know when I’m losing them. When they’re bored, I’ll just mark that passage and come back to it.
Another thing is I’ll literally read the whole thing out loud. If I’m losing someone for some part of it, I can just tell. I don’t even need their feedback.