Turns out there is a disagreement between Amazon and Macmillan over charges for eBooks. Macmillan has asked Amazon to raise the price of the eBook from $9.99 to around $15 but Amazon doesn’t agree and Macmillan books have been pulled from Amazon. Macmillan imprints include Henry Holt, Farrar Straus, and St. Martin’s.
http://bits.blogs.nytimes.com/2010/01/29/amazon-pulls-macmillan-books-over-e-book-price-disagreement/?th&emc=th