Yeah, i noticed the ads, too. I guess a way to keep it free to us users and keep the lights on.
Just reminded myself of ways to save time when reading nonfiction: skip the opening chapters. These are the horror stories and the review of the history of the problem under discussion. Don't need that, I understood what the book was about from the title.
Sometimes I read from the last chapter back till I feel i got enough of their solution tips to shut the book.
R