Penguin USA Group has returned its e-book titles to lending library shelves after just a three day absence. The publisher pulled every one of its titles and also announced it was delaying the release of any of its new books to the Overdrive and Amazon lending services which power America's libraries.

Penguin cited vague "security concerns" but failed to elaborate on them when it returned the books to active circulation this morning. The publisher also has not restarted, nor said when it will restart adding new and forthcoming titles to the services. The publisher set off somewhat of a storm on November 22nd when it pulled its e-books, particularly with librarians across America.