Introduction to Object-Oriented Databases by Roberto Zicari · Published September 1, 1998 · Updated February 16, 2014 Steve Hand and Jane Chandler Very visual introduction to ODBMS. DOWNLOAD (PDF)
The Definite Guide to db4o June 1, 2006 by Roberto Zicari · Published June 1, 2006 · Last modified January 3, 2015
Embedded Databases: The Invisible Engine That Could August 1, 2005 by Roberto Zicari · Published August 1, 2005 · Last modified February 16, 2014
006.03 ODBMS for RDBMS Users January 1, 2005 by Roberto Zicari · Published January 1, 2005 · Last modified February 18, 2014