Ninety-nine percent of a cup of coffee is water, and if you use bad, really bad water, you might just as well throw away this book and buy a jar of instant. If the water is not pleasant to drink, do not make coffee with it. Use bottled water or a filter system. Hard, or alkaline, water does not directly harm flavor and aroma, but does mute some of the natural acids in coffee and produces a blander cup with less dry brightness. Water that has been treated with softeners makes even worse coffee, however, so if you do live in an area with hard water, you might compensate by buying more acidy coffees (African, Arabian, and the best Central American origins) or by brewing with bottled or filtered water. Some automatic drip coffee makers come equipped with built-in filters. Although these integral filters are effective, they seem fussy and over specialized to me. It might be better to buy a filtration system that can be used for all of your water needs, rather than one that is irrevocably stuck inside the coffee brewer.
