I bought Palmer's latest How To Brew, specifically for the water section. He makes a good effort to try to give you what you need to know and present it in the moist usable format. I read it once. Will read through it a couple more times,
So far, too many variables interacting with each other to let me feel like I have wrapped my head around the subject.
I think of my local tap water as pretty hard. I go and buy 10 gallons of filtered drinking water on brew day.
When I read these things, it occurs to me what would be useful, if somebody wrote a water treatise "backwards". Everything I read, they start off in depth about water and PPM and this chemical, and that chemical, and so on. It is not until the end that I learn what the basic problem is. Maybe that is just me and how my peanut brain is organized.