The "OpenCAD - A Step by Step Guide to Developing a Professional CAD Application" book by Deelip Menezes describes in a single book how (with the assistance of the DWGdirect SDK. Focused on a single library and on Windows applications using MFC, but interesting nonetheless. PDF and physical copies are available. http://www.sycode.com/publications/books/opencad/
Info on BIM, CAD & 3D software for architects and students