A page on the Genevan Psalter from The Story of Christian Music, by Andrew Wilson-Dickson, 2003. This overview is rather condescending and simplistic, but the clearest and simplest I've seen.
This book is undoubtedly copyright, but I include this page on the authority of Google, which seems to have scanned in the entire work. My apologies to Mr W-D if this is a problem. I advise readers to buy a copy of the book, which is worth having on your shelf.