Add linear algebra book (#10174)

books/free-programming-books-subjects.md

@@ -434,6 +434,7 @@ Books that cover a specific programming language can be found in the [BY PROGRAM
 * [A Friendly Introduction to Mathematical Logic](https://milneopentextbooks.org/a-friendly-introduction-to-mathematical-logic/) - Christopher C. Leary, Lars Kristiansen
 * [A Gentle Introduction to the Art of Mathematics](https://osj1961.github.io/giam/) - Joseph E. Fields
 * [A Programmer's Introduction to Mathematics](https://pimbook.org) - Jeremy Kun
+* [A Quick Steep Climb Up Linear Algebra](http://stephendavies.org/quick.pdf) - Stephen Davies (PDF)
 * [Abstract Algebra: Theory and Applications](http://abstract.ups.edu) - Tom Judson
 * [Active Calculus](https://scholarworks.gvsu.edu/books/20/) - Matt Boelkins
 * [Advanced Algebra](http://www.math.stonybrook.edu/~aknapp/download/a2-alg-inside.pdf) - Anthony W. Knapp (PDF)