Full Frontal Calculus:
An Infinitesimal Approach
Single-variable calculus, presented with panache: crisp, concise, and with a smoky infinitesimal flavor.
Read the book right here as a free pdf.
After finding you like it, be a mensch and purchase a paperback copy at Amazon for $17. If you don't want a paper copy, but still want to be a mensch, you can sit at the bar and put bread in my tip jar, which accepts PayPal, credit cards, and debit cards.
Other Books
Lobachevski Illuminated
A historical introduction to non-Euclidean geometry developed in the midst of extensive commentary on one the subject's foundational documents: Lobachevski's Theory of Parallels.
Winner of the Mathematical Association of America's Beckenbach Book Prize in 2015.
The book can be purchased at Amazon or from the website of the American Mathematical Society.
Precalculus Made Difficult
Algebra, Coordinate Geometry, Functions, and Trigonometry.
Learn 'em well! The fate of the free world depends on it!
All of high-school mathematics in one 200-page textbook.
Read it right here as a free pdf. If you like what you see, you can support a starving math teacher (or at least one who might have skipped lunch) by purchasing a print copy for $17 at Amazon, or by discreetly slipping some cash into my tip jar.