Grammar & punctuation
The Usborne Book of English Grammar, Spelling and Punctuation
Usborne Publishing 0-74605843-8
Written for children, so basic, but also great revision. Never be frightened of these topics again.
Improve Your Punctuation and Grammar
howtobooks 1-85703-873-8
Suits beginners, but also goes into reasonable depth. A stage on from the Usbornes.
The Penguin Guide to Punctuation
Penguin Reference 0-14-051366-3
Excellent for quick reference or detailed reading. Takes you to an editor's standard.
Eats, Shoots and Leaves
Profile Books 1-86197-612-7
Entertaining, informative, irritating and unreasonable. More for reading than reference. Become an apostrophe anorak. Join the Apostrophe Protection Society.