Background
I have studied matematics for 4 years at the university, both pure and applied, e.g. topology, functional analysis and valuation of Derivative Assets. Currently I'm taking a course called advanced microeconomics, using Hal Varian Microeconomics Analysis. I feel that this book has a lot of explaining text that I would better understand with "pure math definition". E.g. Just defining risk-averse as a concave utility function.
So I wonder if there is book more related to the format of a math textbook that I can use as a secondary book, to get another perspective? I'm asking this question because during my studies I often find myself reading through a lot of text and when I arrive at a mathematical definition in the book or e.g. wikipedia, then I can understand what the author is trying to tell me.
I have looked at this and this questions but both are >2 years old, thus maybe there is something new on the market?