"Eats, Shoots and Leaves" by Lynne Truss. HarperCollinsPublishers, Hammersmith, London, W6 8JB, ISBN 978-0-00-732906-9
This book is a treasure trove of grammatical excellence, giving clear examples of what should and shouldn't be said or written in order to preserve the English language.
Yes, I can hear those in the background averring that any language must evolve to stay alive, but evolution, in Darwinian terms, is not always an improvement; take the koala for example, that is, it has evolved to the point where it can only survive by eating the leaves of one species of gum tree.
Pointing out that the human race is an example of positive evolution is an argument which must provoke such responses as 'the human race has nearly evolved itself out of existence'.
Fortunately language is a topic which won't contribute to the downfall of our species, but current trends in educational attitudes towards spelling and grammar, not to mention a move from handwriting to keyboard, may be contributing to the downfall of our communication processes.
Lynne Truss' work shows, by numerous examples, the effects that grammatical or spelling errors can have on the correlation between the message intended and the message received. Her comments on the use of the comma demonstrate it to be a tool worthy of care and respect rather than random application.