The Penguin guide to synonyms and related words - S. I Hayakawa

Taking 6,000 commonly used - and confused - synonyms, this unique guide is much more useful than a straight thesaurus because it offers both a definition of each word, and then an explanation of how to use it in the correct context. Words of similar meaning are grouped together in helpful thematic sections, making it easier to find just the right one. Offering more detail and more of the subtle nuances of our vocabulary than a thesaurus, this is a reference must for anyone with an interest in language.

'More helpful than a thesaurus, more humane than a dictionary, [it] maps linguistic boundaries with precision, sensitivity and, on occasion, dry wit ... a delightful book' The TLS.