The first mistake that you can make is to take the wrong book.
Reading a book takes lots of time, reading only the best and brightest will save you time and neurons.
The second mistake you can make is to read only one book about the subject you want to learn.
The scientific method first makes hypothesis, test them, then review of confirm the hypothesis, turning it into a theory.
Our mind do exactly the same thing. It has a model of the world, experiment, and redefine the model.
Reading is an experiment, it challenges what you already know (your model) and redefine or confirm it.
Needless to say, only redefinitions make you grow. The more redefinition you make to your model, the more you learn.
When you are reading a book, you are copying the model that the author has.
The problem is that, once you read the book, reading the same book twice, will not redefine your model very much.
Mastery means that whatever you can read about the subject, it does not redefine your model very much.
The best way to keep redefining your model, is to read several of the best material about the same subject. That's what I call cross reading.
You know you get into mastery when reading more of these different material does not redefine your model.