The University of Pennsylvania offers a free series of books called Software Foundations with the following description:

The Software Foundations series is a broad introduction to the mathematical underpinnings of reliable software.

The principal novelty of the series is that every detail is one hundred percent formalized and machine-checked: the entire text of each volume, including the exercises, is literally a "proof script" for the Coq proof assistant.

The series includes Verifiable C, which seems very appealing as a way to avoid some of C's infamous "footguns." I haven't read the series myself, but I might in the future because I like math, logic & programs that do what they're supposed to do.

Are there any materials that would be good as alternatives or complements to this series?

Edit: Adding the Vercors Wiki to the resources in this thread