Strout calls him “Dr. B.” for his magical abilities to ferret out inconsistencies, eradicate inaccuracies and fix convoluted sentences. “Benjamin is all about the ear,” she wrote in an email. “I think the guy is astonishing, truthfully.” So do his 23,600 followers on Twitter, which he calls “the agora of the 21st century,” who know him for his snappy language-related interventions.

This is an excellent time for someone to tell us how to think about these things. Social media has spawned a generation of un-Strunk-and-White-ified people who appear to believe that punctuation is optional, that grammar is for the elderly and that ending a sentence with a period is a deliberate act of aggression.

Meanwhile, the president of the United States thinks “seperation” is a word, once referred to his own wife on Twitter as “Melanie” instead of “Melania” and has explained his personal philosophy of capitalization by declaring: “I capitalize certain words only for emphasis, not b/c they should be capitalized!” (He also uses exclamation points like a text-crazed teenager, but that is another issue.)

The president, whose name Dreyer also would prefer not to say (or to write down), comes in for some deft shade-throwing in several places in the book, as when “unprecedented” is included in a list of sometimes misspelled words. “How hard was that?” Dreyer writes, and Oval Office watchers will recognize an allusion to the president’s notorious “unpresidented” tweet.

Similarly, Dreyer takes The New Yorker, which he refers to as “a certain magazine,” to task for its infamous insistence on using a dieresis — two dots above a letter — in words with double vowels, like re-elect (“reëlect”) or pre-existing (“preëxisting”). “That certain magazine also refers to adolescents as ‘teen-agers,’ ” i.e. with the clunky inclusion of a hyphen in there, he writes. “If you’re going to have a house style, try not to have a house style visible from space.”

“Dreyer’s English” not only lays down rules but offers tips for writers who want to be clear and elegant as well as correct. Common pitfalls in fiction, Dreyer writes, include muddled timelines and geographic sloppiness; using fancy synonyms for “said”; giving similar names to too many characters — it has always annoyed him, he says, that “Downton Abbey” needlessly features two people named Thomas — and peppering your writing with show-offy allusions to “underappreciated novels, obscure foreign films, or cherished indie bands.”

“A novel is not a blog post about Your Favorite Things,” Dreyer notes.

Other tips: Cut back on “suddenly” and “began to.” Be vigilant for such phrases as “Rob commuted to his job,” with its amusingly jarring inadvertent rhyme. Don’t use “curate” “to portray what you’re doing when you organize a playlist of motivating songs for gym use.” And: “Go light on exclamation points in dialogue. No, even lighter than that. Are you down to none yet? Good.”