ohfor07
Have not read all of her books, but starting with her first - The Cure For All Disease, Clark does cover the Zapper. The first was originally written sometime around the 80s - 90s, but has been revised at least 4 times since. In it she starts off with telling about the R&D she did that eventually lead to developing the first generation Zapper; she also provides simple DIY instructions for pretty much any non-technical, un-skilled person to make their own (using a shoe box as the unit's case), then goes over the basics of how to use it, and finally at various places throughout the remainder of the book she provides anecdotal evidence of the successes people had in using it.
It is interesting that she has not written a book (at least not yet as far as I'm aware) that focuses entirely on the Zapper, especially with regards to the recent years when it seems the increased curiosity by the public could really benefit by it's inventor (
Hulda Clark ) telling all she knows about zapping.