Kappa Books announced Thursday that it has acquired Modern Publishing, a division of Unisystems that has been in the coloring and activity business for more than 40 years. The two companies’ operations will be merged, but Kappa will retain the Modern name and will market Modern’s line of mass market children’s books through a new division headed by longtime Modern president Andrew Steinberg.

“We decided it’s time,” Steinberg says. “It’s become more and more challenging to do what we do. We wanted a partner that understood the business and could make it work. They have the printing strength and the distribution strength, and we have the licensing strength. It’s about taking both of our skill sets and merging them.”

Kappa’s core business is puzzle books, but it also sells reference titles and some coloring, activity, story and other children’s books. It holds the Sesame Street license for a line of board books, as well as Woman’s Day, Chicken Soup for the Soul, and TV Guide for puzzle book series. The acquisition will add Modern’s Lisa Frank, Fisher Price, Hot Wheels, Zhu Zhu Pets, Hello Kitty, Smurfs, Lalaloopsy, and other licenses to Kappa’s portfolio.

Kappa has been in acquisition mode over the last two years, purchasing the intellectual property of another mass market children’s book specialist, Playmore, and taking a minority stake in Bendon Publishing.