When I was young, I have read more than half of them. They should better be read in order, starting with the theory of sets. I do not believe that they are us

When I was young, I have read more than half of them. They should better be read in order, starting with the theory of sets. I do not believe that they are useful for learning for the first time some part of mathematics, but they are useful to revisit already known parts, to think about them while examining a more rigorous or alternative exposition of the concepts. Some of the books also contain interesting facts about the history of mathematics. See the Wikipedia descriptions, e.g.: https://en.wikipedia.org/wiki/%C3%89l%C3%A9ments_de_math%C3%A9matique https://en.wikipedia.org/wiki/%C3%89l%C3%A9ments_de_math%C3%... Especially if you can read French, you can find many of the books on archive.org.