This book was lent to me by my manager at work. I should point out that this was not because of any punctuational slackness on my part, but as a result of my discussion of the Oxford comma a few weeks ago. It's a volume that seems to instil strong reactions, both positive and negative; unsurprisingly, I enjoyed it. It would be a mistake to assume that Truss is against progress (though she does seem to return frequently to Gertrude Stein as some sort of punctuational Antichrist); she accepts that change is constant. The main message is that many punctuation errors result in ambiguity at best, or change semantics at worst.
My only recollection of grammar at school is of endless lessons about the apostrophe - for which the rules are, frankly, among the more simple (though "pluralisation of words such as do's and don't's" is perhaps a bit aethereal for the more mundane reader - what is pluralised elsewhere, if not words?). This is where Truss begins, before moving on to commas (and the legal lack thereof), colons and semicolons, dashes and hyphens, question marks and exclamation marks. As well as recounting howlers, there is some clarification of rules, including more grey areas where stylistic choices may be made. It's also educational in a historic sense, with some exploration of the emergence of punctuation. In particular, the publisher accredited with the early introduction of punctuation in print is one Aldus Manutius - whose first name I recall from the company that originally released PageMaker, and whose last name will of course be remembered by anyone who has read Foucault's Pendulum.