This is great book on the fundamentals of electricity, batteries, electromagnets, LCD & Dichromic displays & meter use, testing & calibration. Henry, did a very good job describing these basic fundamentals so the older watchmaker could stay up to date & keep repairing & servicing watches & small clocks. It would be a good introduction book for a young student interested in electricity & some light experimentation or as one newspaper put it:" Inquiring minds want to know". Sad to say though Henry passed away several years back. The industry lost a good educator.