One resource that many people could use is Bibliocommons . This is the on-line catalogue that many libraries in the US, Canada, Australia, and New Zealand now use. People write comments or reviews of books using Bibliocommons and can create reading lists and do some social sharing through it.
While there is no guarantee that Amazon won't buy it, too, it doesn't seem very likely. Here is a link to their about page:
http://www.bibliocommons.com/about/about-us
I use my public library as my entrance into it.