A book on punctuation marks from ancient Greece through Google sounds duller than a worn-down pencil. But as Keith Houston proves with Shady Characters, you can’t always judge a book by its topic. The Scottish author possesses all the virtues of dry British wit (the ampersand is “another of those things the Romans did for us”) and applies them to subjects that should interest anyone who cares about language. Sifting out the history of # leads to the derivation of “pound” from the Latin “to weigh,” which links to the weight of silver coinage and leads to Britain’s pound sterling (£). The trusty hyphen shares Shady Characters with the interrobang, a ‘60s combination of ? and ! largely ignored by writers and publishers but has found fans, like so many other obscure things, on the Internet.