Prelude to Mathematics by W.W. Sawyer was written to give students an overview of modern math concepts beyond algebra. Topics include non-euclidian geometry, linear algebra, projective geometry and group theory. Again, for someone with an understanding of algebra. I enjoyed it and think it's in the spirit of what you're looking for.
Edit: Introduction to Graph Theory by Trudeau is another that I really liked. Very little was applicable to graphs as programmers think of them. Pure math that is easy to grasp and enjoy.
I came to add add Introduction to Graph Theory and found it here. I second it! A nice book and I appreciate it's funny introduction as a book designed for liberal arts majors injured by the pedagogy of institutional mathematics (paraphrasing).
If you have a grasp of algebra and sets this book is an easy read for the curious or mathematically immature.
Edit WhatIsDukkha is correct and their suggestion better reflects what I intended to say.
Edit: Introduction to Graph Theory by Trudeau is another that I really liked. Very little was applicable to graphs as programmers think of them. Pure math that is easy to grasp and enjoy.