very helpfull tnx Robert

It's a way of saying that you don't need to be intellegent to understand the book. There's a (somewhat) related expression: "Teach it to me (or tell it to me) as though (or like) I was a 6 year old." Which is to say, pretend I don't know anything, and explain it to me, including what you think I already might know.

It means even an idiot can understand it,that is to say,you can learn how to manage your time easily by following the book.

Some sort of saying "managing your time for dummies"