But like the rest of the book publishing industry, Harlequin is dealing with declining revenue and income, a product of the continuing shift toward digital books. The mass-market, grocery-store paperback, long the company’s bread and butter, is rapidly disappearing.

Harlequin also missed out on what was perhaps the biggest romance-book phenomenon in modern history, “50 Shades of Grey,” which was originally released by a tiny publisher in Australia before being acquired by Random House’s Vintage Books division. (In 2012, Harlequin’s chief executive said that sales of the “50 Shades of Grey” series had totaled more than its entire North American retail division.)

The trilogy of erotic novels helped increase the popularity of romance books in general, but it did not necessarily bring more readers to Harlequin. At the same time, as the genre’s appeal grew, more and more romance writers were trying their hand at self-publishing.

News Corporation’s purchase of Harlequin is its largest acquisition since the company was separated from the more lucrative film and TV business, 21st Century Fox, last summer. Adding Harlequin, which will be folded into the company’s HarperCollins book unit, is consistent with the company’s broader strategy of investing more heavily in the publishing industry. In 2011, the company bought the religious publisher Thomas Nelson Inc. In 2012, it tried to buy Simon & Schuster from CBS, but the two companies could not agree on terms.

More generally, the book publishing industry is in the middle of what is expected to be a protracted period of consolidation, spurred by the growing popularity of e-books and the increasing power of Internet retailers like Amazon, Apple and Google. To negotiate more effectively with these retailers, publishers have been compelled to join forces.