The biggest trade publishers continue to get larger: Hachette Book Group has entered into a “binding commitment” to acquire one of the industry’s largest and most distinct independent publishers, Workman Publishing. HBG, backed by its parent company, Lagardère, is paying $240 million for Workman, which had sales of $134 million last year. The deal is expected to be completed by the end of September.

In making the announcement, HBG CEO Michael Pietsch called Workman “a brilliant publisher, the most creative in the industry,” that pioneered the method of combining images and information in a distinct way. That approach has led to such hugely successful franchises as the What to Expect and Brain Quest series as well as Page-a-Day calendars.

When the acquisition is completed, Workman Publishing will become HBG’s eighth publishing group, comprising the imprints Workman, Algonquin, Algonquin Young Readers, Artisan, Storey Publishing, and Timber Press. (The publisher has about 300 employees scattered across offices in New York City, Chapel Hill, N.C., North Adams, Mass., and Portland, Ore.) The new group will be led by Workman Publishing’s current CEO, Dan Reynolds, who will report to Pietsch and join HBG’s executive management board. Carolan Workman, executive chair and president of the company—who has been heading the publisher since 2013, following the death of her husband, company founder Peter Workman—will retire following the completion of the deal.

In an interview with PW, Reynolds said finding a new owner for the company, founded by Peter Workman in 1968, had been in the works for a few years. Reynolds said Carolan Workman’s “#1 priority in finding a new home for the company, even over price, was the security of our employees, and we have found that with Hachette. They understand what makes us tick.”

Pietsch told PW that, given that most of Workman’s most popular books and products have been developed in-house, HBG would be “crazy” to interfere with the company. “They have a unique culture,” Pietsch said.

HBG and Workman fit together in many business ways. Workman is backlist-driven, with Reynolds saying that at some of its imprints, 70% to 80% of revenue is generated by its backlist. Despite acquisitions and organic growth, HBG has continue to look for ways to expand its backlist, and Pietsch praised the quality and depth of Workman’s roughly 3,500-title backlist.

With its unique approach to publishing, Workman has maintained it own sales force, and has sold its line far beyond bookstores. Both Reynolds and Pietsch said that they see a big opportunity in reaching those markets with a broader list from the combined companies.

Another practical reason for the deal, Reynolds said, is that it costs of a good a deal of money to invest in the type of publishing Workman does. Freed from the distraction of maintaining its own infrastructure, he said, Workman could devote its full attention to developing new products.