Lee Ambrosius (http://hyperpics.blogs.com/beyond_the_ui/) has a VBA book in progress and it is now at a staggering 26 chapters and 450 pages. It appears to be very thorough judging from his outline of chapters posted to his blog. Knowing Lee it will be very detailed with many examples for those learning VBA or already VBA programmers for AutoCAD. Lee states he plans to release it within the next few months.
Link to Lee's VBA Book post http://hyperpics.blogs.com/beyond_the_ui/2005/02/vba_book_projec.html