Apple and five of the biggest U.S. publishers are accused of colluding to raise the price of electronic books for e-readers including iPad, Kindle and Nook.

The Wall Street Journal reported the Justice Department has warned it plans to sue Apple, Penguin Group, Simon & Schuster, Hachette Book Group, Macmillan, and HarperCollins. But people familiar with the matter told the paper a settlement may be in the works for some of the publishers, which could lead to cheaper e-books.

Though the devices cost hundreds of dollars, many e-books are cheaper than the traditional paper versions

The Hunger Games, by Suzanne Collins, published by Scholastic, is $5.51 for the Kindle and $5.51 for a paperback version on Amazon.  The book is $8.49 on the Nook.

Moneyball, by Michael Lewis, published by W. W. Norton & Company, is $8.29 on the Kindle, $9.72 in paperback through Amazon with a list price of $15.95. Barnes and Noble's Nook version is $8.29.

But not all e-books are a big savings over the dead tree version. Ken Follett's 865-page "Fall of Giants" is $18.99 on Amazon for the Kindle yet the hardcover version is $20.63.  Lone Wolf: A Novel, by Jodi Picoult is $14.99 on Kindle but $15.99 in hardcover.

The iPad 2 retails for $399 while the new iPad announced this week starts at $499. Amazon's Kindle starts at $79 while the Nook retails for $99.

About 28 percent of U.S. adults, or three in ten, use an electronic reader device, according to a survey by Harris Interactive released this week. That's almost double the 15 percent who said they used the device in the summer. In the most recent survey, 72 percent said they do not use a device, down from the 85 percent who did not last summer.

Almost three-quarters of e-reader users are reading six or more books in an average year. Among those who are currently using an e-reader, 29 percent say they typically read more than 20 books in an average year, while 21 percent  say they read between 11 and 20 books and 24 read between 6 and 10 books.

Three in five non e-reader users are reading five or fewer books on average in a year. Among those who do not use that device, 18 percent typically reads no books in an average year, 19 percent typically read between one and two books and 21 percent typically reads between three and five books.