It’s one of the more divisive habits among bibliophiles: to write in the margins of a book, or not? Is the act more subversive for being done in pen rather than pencil, or in the pages of a freshly printed hardback, rather than a secondhand paperback? Marginalia, the grand-sounding name for what is often a juvenile activity, can both delight and enrage, depending on who has created it and where. 

As long as books have had margins, there has been marginalia. The scholars behind medieval textbooks littered the edges of their curlicued text with drawings of everything from disgruntled unicorns to monkeys playing the bagpipes. Noteworthy examples of more recent jottings: Vladimir Nabokov neatly going through 55 Short Stories from The New Yorker, 1940-1950 in pencil and grading each story...