As a FAA licensed A&P maintenance technician, I was expecting far more than the generic info that most A&P's receive with their training. Most of the content covered how the avionics worked. While there was some diagnostic/troubleshooting, it was at a very low level and did not go into much detail. There was a lot of text that could have been much more definitively explained with a flow chart. The normal repair info provided was to ship the possible defective unit back to the manufacturer for repair. In one word, what this book lacked is DETAIL!
In all fairness to the author, avionics diagnostics and repair is not an easy subject of cover. The cover says that the audience is for Pilots and Technicians. Having two diverse audiences is probably the problem. There is probably slightly more info than what is needed by the Pilot. However, the info is highly deficient for the Technician. This book is more of a Pilot book.