A friend of mine wrote this nice book on Foundation Repair which she made available online and for free.
It has a lot of useful information about types of soil, common causes of foundation problems as well some of the technologies available to fix them. It is written in an everyday language, and full of pictures, so you do not need to be a structural engineer to understand it.
I hope that helps you answer a lot of questions about foundations without the sales pressure so that you can make an informed decision about your home's foundations.
The link below gives you option to read it online or download the whole book in pdf, absolutely free.
Foundation Technology: Your Guide to What Goes Under Your Feet