The Water Heater Workbook is the bible of water heater maintenance. It was written by Larry and Suzanne Weingarten with many illustrations by John Middleton.

There are sections on how water heaters work, gas and electric controls, judging a tank's condition, anode replacement, sediment control, tankless heaters, solar equipment, heat pumps and much more, as well as an excellent troubleshooting guide.

The price: $20, which includes shipping, and for California residents, sales tax.