One of the most complete guides to individual historic sites to be found in Cornwall and Scilly, and is ideally suited to those wishing to visit the sites themselves.
Craig Weatherhill (1950 or 1951–2020) was a Cornish antiquarian, novelist and writer on the history, archaeology, place names and mythology of Cornwall.
This is a fine book--clear, well written, and helpful, whether you only want to read about ancient Cornwall or are hell-bent to visit the sites yourself.
Excellent lengthy introduction to prehistoric sites with a substantial gazetteer that, unfortunately, is almost impossible to navigate being an alphabetical list for various notional areas of Cornwall...