As the market quickens for “e-books,” the schedule for their release is slowing down. Simon & Schuster announced Wednesday that the electronic editions for more than 30 works coming out in the first half of 2010 would not be available until four months after the hardcover. The affected books include novels by Don DeLillo and Mary Higgins Clark and a memoir by Karl Rove. HarperCollins spokeswoman Erin Crum said the publisher plans to withhold the digital version of five to 10 titles per month, starting next year. And Hachette Book Group USA will delay a “wide selection” of e-books in 2010, spokeswoman Sophie Cottrell said. Publishers and authors have worried that e-books might hurt sales for hardcovers; Amazon.com, Barnes & Noble.com and other online retailers commonly price top-selling e-releases at USD 9.99, which publishers say is too low and could cheapen the value of books overall. Simon & Schuster CEO Carolyn Reidy said Wednesday that the rise of e-books has led to a “cannibalizing” of new hardcover purchases. E-books do expand the market for older books, Reidy added. Readers buying a new fiction work are inspired to buy many of the same author’s previous books, or “backlist,” in digital format because of the ease of ordering. Previously, buyers might have gone to a retail outlet and bought just one backlist title, she said.