Mathematics is not learned by reading books. One becomes a research mathematician by solving problems. Most people need an adviser to recommend a good problem. Then you start thinking and reading what is relevant to your specific problem. General education by reading books with hundreds of pages can be done as a parallel process, but the main emphasis should be on a specific problem. It is a duty of 
the adviser to find a problem which does not require too much reading.

There are many examples that demonstrate these principles. Many good mathematicians obtained their first original results before the age of 18 or even much earlier,
at the time when
they learned very little.

Myself, I published my first paper at the age of 18, when I was a second year undergraduate student. I did not know much of mathematics at that time. I do not say that this paper is among my best, and at present I would not publish such a result, but this is irrelevant. The main point I am trying to make is that one has to solve problems, not to read books. It is not necessary that problems you solve in the beginning are new/publishable. But eventually you will obtain new results.
Finding a good adviser is a crucial matter, for most people.