Grolier is one of the largest American publishers of general encyclopedias, including The Book of Knowledge (1910), The New Book of Knowledge (1966), The New Book of Popular Science (1972), Encyclopedia Americana (1945), Academic American Encyclopedia (1980), and numerous incarnations of a CD-ROM encyclopedia (1986–2003).

As an educational publishing company Grolier was known for its presence in school libraries and its in-home encyclopedia sales. It also had a strong presence among parents of children under six years old, the market for Grolier's direct mail-to-the-home business.

In June 2000, Grolier became part of Scholastic Corporation, which now maintains Scholastic GO, formerly Grolier Online. Since 2007, the Grolier imprint Orchard Books has published the Rainbow Magic and Beast Quest series in the United Kingdom.