This article is from the alt.usage.english FAQ, by Mark Israel firstname.lastname@example.org with numerous contributions by others.
"The Oxford Companion to the English Language" (ed. Tom McArthur,
Oxford University Press, 1992, ISBN 0-19-214183-X) is an
encyclopaedia with a wealth of information on various dialects, on
lexicography, and almost everything else except individual words
and expressions. "Success With Words" (Reader's Digest, 1983, ISBN
0-88850-117-X) is especially suitable for beginners.