This link for a downloadable creative commons book on the subject of terrain modeling is available to download.

https://tudelft3d.github.io/terrainbook/

Its very broad covering almost every conceivable topic about the implementation of modeling terrain on computers. But its not tremendously deep in any one topic. But it does have references to material and a large bibliography to reference more depth and papers where I expect the hard math is in there.

But this book is a great resource and I would encourage anybody interested to have a look at it. The first few chapters cover the most basic stuff and is highly accessible to non programmers.