Some publishers are moving to larger type to suit the needs of aging readers of mass-market paperbacks.

NEW YORK (CNN/Money) - They call them pocket-size books, but that name may no longer fit as some mass-market paperbacks get bigger.

Publishers are increasing the size of mass-market paperbacks to suit aging readers who find it harder to read the small type of mass-market paperbacks, according to a report published Friday.

The New York Times said two of the biggest publishers of the popular pocket-size books are increasing the size of their books to make room for larger type and more space between lines.

"We've been losing the foundation of our customer base because their eyesight is getting worse, and the books are getting harder and harder to read," Jack Romanos, the chief executive of Simon & Schuster, told the newspaper.

Viacom (Research) unit Simon and Schuster, whose Pocket Books division introduced the mass-market paperback format in the United States in 1939, as well as the Penguin Group, have both started issuing new paperbacks by some of their most popular authors in the bigger size, the newspaper said.

The Times said that while the width of the new books has stayed the same at 4-1/4 inches, the height has increased by three-quarters of an inch to 7-1/2 inches. The longer page allows publishers to increase the type size by up to a half-point, to 10-1/2 points, and to increase the space between lines to 14-1/2 points from about 12, the report said.

More mass-market paperbacks are still sold each day than any other type of book, but that number has steadily dropped for a decade, the report said, citing the Book Industry Study Group, a publishing trade group.

The newspaper said that at a time when sales of ready-made reading glasses are up, the change is meant to meet the needs of those who buy and read paperbacks.

"We've gotten so many letters and e-mails from readers saying, 'Thank you for making the type larger,' " Leslie Gelbman, the president of mass-market paperbacks at Penguin, told the Times.

Readers who want the larger-type format will have to pay a little more, however. Publishers have raised the cover price of the new books to $9.99, $2 to $3 more than the traditional paperback but still less than the $14 cover price of the digest-size books, known as trade paperbacks, that are now the primary format for nonfiction books and literary novels, according to the report.

But big discount retailers, including Wal-Mart Stores (Research), have objected to the higher price of the new paperbacks and ordered smaller-than-normal volumes of the books because of doubts whether their customers would buy as many, the newspaper said.

While some readers have complained about the new format, saying it feels clunky and is difficult to hold, others say they like the changes, the Times report said.

Some publishers, such as Bantam Books, which tried a similar experiment in the late 1980s but abandoned it after issuing about several titles, remain skeptical about the changes, the Times said.

The newspaper said others argue the mass-market segment is in danger of withering without the change. "If you go back 20 years, the mass-market paperback was really driving the business," Romanos of Simon & Schuster told the newspaper. "As long as we have to continue to pay what we do for brand-name authors, we need a healthier paperback format to make it work."

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