While Eves' Foundations and Fundamental Concepts of Mathematics is certainly a bit outdated by now – it is 1997 reprint of a textbook originally published in 1990 – it was still fun and interesting to read.
The books offers a nice historical overview of fundamental concepts of mathematics (hence the title) that includes not just the historical background but a solid introduction of each concept itself. Of course, solid means here that the introduction just provides as much depth as is needed to understand what it is all about. As such the different chapters may whet one’s appetite for more on the respective topic. Just when it gets interesting the text stops. It has to. Otherwise, Eves would not be able to cover as much as he does.
Sometimes maybe, the little detail that is given can also already seem a bit too much. Getting to a theorem 48 in just one chapter shows that Eves is certainly not just skipping over details when he feels the reader may benefit from a rigorous presentation of the material.