I started with Vision in Elementary Mathematics, then read Mathematician's Delight (mentioned in this post). At some point, I may have read Prelude to Mathematics. They're all great, but I read them when I was too busy to write up a detailed review. (I'm getting frustrated by the hodgepodge state of my bookshelves. I want to be able to find these three books, so I can say more about them.)
Now I've just finished What Is Calculus About? Also fabulous. I wondered what else the great W.W. Sawyer had written, and found this lovely archive.
I'm glad to see he agrees with my assessment of limits:
The first chapter dealt with limits. No one sees any reason for thinking about limits before having some exposure to calculus, so I left chapter 1 for much later in the course. (from http://www.marco-learningsystems.com/pages/sawyer/illinois.htm)
I also liked Notes on the art of passing exams.
So here was this great teacher, very aware of the issues we discuss on blogs - being less helpful, project-based learning, etc. - and yet I had never heard of him until recently. His books sold widely when they were first published, but now are treasures we uncover.
It's so sad to think of these wonderful books sitting on bookshelves, unknown. And it's exciting to know how much the internet helps us learn about good resources, however old they are.
I just got my copy of W.W. Sawyer's A Concrete Approach to Abstract Algebra in the mail. I would love to work through it together with a few friends. Anyone interested?