Nearly 400 illustrations, diagrams and tables all produced with Inkscape. I even used Inkscape to produce better looking versions of graphs generated my math programs!
The illustrations are all line art with flat tones (this works best with the printing process chosen - especially at the reduction needed for this project). Not the sort of thing most of you guys like, but Inkscape is really, really good for line art (I know many of you like photorealism and don't appreciate the minimalist appeal of B&W line art

So many thanks to all of the Inkscape developers - you have a great program here!
I haven't put a link in to amazon as the book is a commercial project. If you want to look at it you can search for The Hot Air Balloon Book on Amazom.
fizzcat