The North American Grasshoppers, volume I, Acrididae, Gomphocerinae and AcridinaeBy Daniel Otte
This is a very thorough treatment of the Slant-face Grasshoppers. It is full of information on behavior, has descriptions and maps of all species, as well as high quality illustrations of nearly all. It is extremely useful as an identification guide, as well as for learning about these fascinating insects. It covers all of North America from Panama northward. The treatment is still nearly up to date, with little having changed since it was published. I believe it is out of print now, but I find it still occasionally available. Hopefully it will be reprinted.
Harvard University Press