GNU/Linux Desktop Survival Guide
by Graham Williams
Once you get into writing code you will need the GTK+/Gnome API documentation and might find the tutorial at http://www.gtk.org/tutorial/ and the API documentation at http://developer.gnome.org/doc/API/api-toc.html useful.
You can find an introductory article on using with Python at http://www.linuxfocus.org/English/July2000/article160.shtml.
Some useful books include:
Beginning GTK+ and Gnome Programming, by Peter Wright, 613 pages, published May 2000 by Wrox Press, ISBN 1861003811. Covers glib, Gtk+, and Gnome. Also covers Glade but rather skimpily. Suitable for the beginner.
GTK+/Gnome Application Development, by Havoc Pennington, 492 pages, published August 1999 by New Riders, ISBN 0735700788. Provides extensive coverage of the GTK+/Gnome APIs and is a good guide to getting up and started with Gtk+/Gnome.
Developing Linux Applications with GTK+ and GDK, by Eric Harlow, 512 pages, published February 1999 by MacMillan, ISBN 0735700214. Provides a basic introduction to using the GDK and GTK+ toolkits, but not the Gnome toolkit.
Teach Yourself Gtk+ Programming in 21 Days by Donna Martin, et al.
GTK+/Gnome Application Development by Havoc Pennington.
Gnome/Gtk+ Programming Bible by Arthur Griffith.
Linux Application Development by Michael K. Johnson, Erik W. Troan.