Diamond Book Distributors has announced that it is now the exclusive U.S. distributor of books published by Checker Book Publishing Group to the bookstore, library, warehouse, mass merchandise, and direct markets.  Checker had previously had a non-exclusive relationship with Diamond, and was also using Midpoint (see 'Diamond Book Division Grabs a Gaggle of Publishers').  The agreement does not include non-direct accounts in Canada and the U.K.