For me the most essential series of books for looking up classical recordings has been the Penguin Guide series. My first one, from 1984, is titled The Complete Penguin Stereo Record and Cassette Guide, it then transitioned to The Penguin Guide to Compact Discs and is nowadays more simply called The Penguin Guide to Recorded Classical Music. It is worth finding some of the older ones as well as a brand new 2010 edition because recordings are often deleted and the old guides provide a valuable reference to them. I now have six of them, collected over the years.
They have all been compiled by Edward Greenfield, Robert Layton and Ivan March and are fantastic tomes for dipping into or referencing whenever you fancy buying a new recording of a classical piece. Written in a style understandable by all, they describe the performances and recording quality in a way that gives you a decent insight into them and use a simple star and rosette system to classify them by quality.
http://www.amazon.co.uk/Penguin-Guid...5&sr=1-1-spell