Honorable Company by Allan Mallinson.
The Haunted Monastery by Robert Hans Van Gulik.
This is one of Gulik's Judge Dee mysteries, set in ancient China. Very good.
Ada 95: The Craft of Object-Oriented Programming by John English, online edition.
A good introduction to Ada 95.
I've been looking at GtkAda, an Ada binding for Gtk+. It's pretty complete, and is portable between Unix and MS Windows, with a MacOS X version in the works. An explanation of how to create the environment for you'll need for using recent versions (Gtk+-2.2.x based, from CVS) with recent versions of GCC under MS Windows is available. (Update: a new binary release makes things much simpler.)