"The following two electronic books (PDF) may be downloaded from Microsoft for free:
First Look 2007 Microsoft Office System (5.93 MB)
"First Look 2007 Microsoft Office System" is a 213 page print & text copy restricted PDF that "helps you get a sense of the huge range of changes and enhancements in the Microsoft Office system". i.e. it's looks like a MS Office 2007 101 type of book.
"7 Development Projects for Microsoft Office SharePoint Server 2007 and Windows SharePoint Services Version 3.0" is a 236 page print & text copy restricted PDF that is a Developer focused intro into SharePoint 2007.