Keith Houston is not a writer by profession, nor is he a trained historian, grammarian, or linguist. Frankly, the Edinburgh-based software engineer is as surprised as anyone to have written a book charting two thousand years of punctuation.

But he has. Titled Shady Characters: The Secret Life of Punctuation, Symbols, and Other Typographical Marks, the account is out today via W. W. Norton—just in time for National Punctuation Day. And like any great twenty-first century literary endeavor, it began with a blog, which shares a name with the book.

"I think it was 2009, [and] I was a software engineer," Houston told The Atlantic Wire in an interview. "As a software engineer, you deal every day with invented languages." Plus, he'd developed a casual interest in typography while typesetting promotional materials for his band. So his friends recommended him a few books.

"One of them was called The Elements of Typographic Style—a play on Strunk and White. It really is amazing," he gushed. The other was Eric Gill's An Essay on Typography, through which Houston became fascinated with the pilcrow ( ¶), an antiquated paragraph mark. Soon he began digging into the histories of the ampersand (&), the cruelly unnamed @ symbol, and the interrobang (‽), a little-used exclamation point/question mark hybrid.

"By I think the end of 2010, I'd written a few chapter-length drafts," recalled Houston, as if nothing could possibly be easier. "I wrote them with some vague idea that I'd do something with them." Not knowing quite what else to do, he threw them on a blog, recruiting a friend for some editing assistance. "Shortly after that, I got a couple of emails from agents who were like, 'Would you be interested in turning this into a book?'"

He said yes—and so an anonymous engineer writing medical imaging software for Toshiba became a published expert on centuries-old items of punctuation.

Houston describes the result as "a sort of popular history of writing," which is about right. To tell the stories of punctuation, it turns out, is also to tell the stories of the myriad technological advances that have facilitated—and continue to facilitate—language in its written form.

The asterisk (*) and dagger (†), for instance, grew largely out of the symbols the grammarian Aristarchus of Samothrace placed in the margins of works of Homer to note lines of questionable origin; the em dash (—) nearly drifted into neglect when typewriter keys forced typists to turn to the double-hyphen (--) instead, but was subsequently validated by modern word-processors. And the Internet plays a tremendous role in the drama as well: the octothorpe (#), for example, fell into obscurity before Twitter resurrected it as the devilishly popular hashtag.

In other words, Houston's Shady Characters covers a tremendous amount of historical and topical ground—veering from ancient Greece to a 1960s Madison Avenue exec seeking to jumpstart a new punctuation mark, from the Protestant Reformation (Martin Luther's Ninety-Five Theses played a minor role in the development of the asterisk) to online communities, where numerous would-be pioneers have proposed an irony or sarcasm mark. (A huge success, obviously.) Naturally, the writer's research took him all over.

"You start with the Internet, you start with Wikipedia, and you wind up going through all these rabbit holes," he said of his process.

In one instance, he set about researching the Interrobang and, unbeknownst to him, ended up chatting with the widow of its creator, "a sort of old Manhattan socialite lady" who is "still is as much of a champion of the interrobang as anyone else is." ("I think that was just a really nice example of the kind of people I talked to," Houston laughed.) Not long after, he received a massive pile of photocopies pertaining to the symbol from a museum of corporate history in Delaware.

Houston has already written a proposal for his next book, which is confidential (though "not entirely dissimilar to this," he confessed). But he's not quite done yet obsessing over punctuation marks, obscure and ubiquitous alike.

"Just today I was writing about irony marks—there's a Dutch one, and just looking at it, it's just a lovely little mark," he said. "I've been emailing the guy who designed it, and he seems like a nice guy. It's just a pleasing little mark. And it's kind of a shame that it probably will never catch on."

Photo of Houston: Cate Gillon for W. W. Norton & Company