Just yesterday reports emerged that Amazon.com had signed new deals with two of the big publishing houses, Simon & Schuster and HarperCollins, allowing them to set higher retail prices on electronic books — mirroring the terms that Apple is offering publishers for e-books on the new iPad. But some of the other major publishers are hitting some disruptions with Amazon.

Pearson plc's Penguin hasn't reached a deal with Amazon. Amazon is still selling Penguin e-books released prior to today, but has stopped selling new ones. The online retail giant has also — temporarily — removed the buy button from e-books from Lagardere SCA's Hachette Book Group. It's a sign that Amazon is continuing to wield its vast market power as the nation's largest online bookseller in its negotiations with publishers ahead of the iPad launch.

Here's more on the e-mail that Penguin sent to literary agents and authors about the situation, from Publishers Weekly:

In a letter to agents and authors, Penguin CEO David Shanks explained that Penguin has reached new terms of sale agreements with a number of e-booksellers, but not Amazon. "Our conversations with Amazon are ongoing and we do hope to continue our long-time relationship with them," Shanks said. Shanks noted that new Penguin e-books "are available through Barnes and Noble.com, Sony, Kobo, eBooks.com, reader applications on the iPhone and soon on the iBookstore for the iPad. Additionally, we're working with our digital delivery partners (Ingram, Overdrive, and Baker & Taylor) to make your eBooks even more widely available." He added the sales of print books are not affected by Amazon's actions regarding new e-books.

In the case of Hachette, Amazon is calling the removal of its e-books a temporary situation. Here's a note posted by "The Amazon Kindle team" on the Kindle Community page:

We recently signed an "agency" agreement with Hachette and we are working with them to offer their books under these terms in the coming days. This means we will not be selling Hachette ebooks in the interim. Update: Hachette has disallowed the sale of ebooks except on agency terms effective as of 12:01 am this morning. We came to terms late last night but we cannot be operationally ready to sell their ebooks on agency terms until two days from now -- April 3 -- when we will also cut over for the other publishers that are switching to agency. If we can get a two day extension from Hachette to continue selling their ebooks under the prior terms, we can have the Hachette ebooks promptly back for sale today. If not, then they will be back on April 3.

Apple is using that "agency" model with publishers, letting them set prices ranging from $12.99 to $14.99 on digital versions of most new release titles. Amazon, which has dominated the early market for e-books, favors a $9.99 standard for such e-books. But Amazon has been forced by Apple's entry into the market to capitulate to some publishers on the higher-price system. The negotiations have intensified ahead of iPad's scheduled launch April 3.

Amazon removed the buy buttons on all books from Macmillan in January during a spat with that publisher over e-book prices. While Amazon ultimately conceded it would have to agree to Macmillan's terms and eventually restored the titles, the interruption likely caused Macmillan some pain.

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