Publishers Weekly says:

In an unexpected development, Penguin USA has announced that it is pulling new titles from library ebook vendors, such as Overdrive. In a statement provided to Library Journal, a Penguin spokesperson said, “[d]ue to new concerns about the security of our digital editions, we find it necessary to delay the availability of our new titles in the digital format while we resolve these concerns with our business partners. ”

PW goes on to note: "The pullback of Penguin from the library market means that four of the “Big 6″ publishers no longer make their frontlist titles available to libraries in digital form." This is not helping things: Withholding e-books from libraries will only inspire people to pirate e-books. It's not going to suddenly make print books more attractive to e-book customers or teach readers a valuable lesson about DRM. This is a real shame.