A number of folks are working on a BizTalk Server 2004 book. It definitely won't be out in January (I wish I had more time to write these days), but it should available sometime in the first half of 2004. 

http://search.barnesandnoble.com/booksearch/isbnInquiry.asp?userid=2VDUNERQM9&isbn=0672325985&itm=1