...X-10 for dummies.
Maybe it is time for such a book. Put a $10-20 price on it and then toss it in free with a starter kit of X10 products.
The most usefull information I've read is online. Unfortunately not all in the same place.
The book would need to cover the basics in the early chapters but also include chapters on noise filters (discusing the different kinds), phase couplers (including the pros and cons of do it your self solutions), macro examples, cameras with setup examples, etc. Last but not least a common problems chapter including cross references to chapters with more detailed descriptions.
eg. Line phases: If people understood what phases were and how it often means that your signal has to take a round trip to the street they would be more understanding of the value of having a phase coupler.