Paul Stewart and Chris Riddell have collaborated on a number of books together, predominately the widely popular (particularly in our household) Edge Chronicles series for ages 10-14 (approx), and the Far Flung Adventure Series (of which, Corby Flood is book 2) for slightly younger readers. 

The Edge Chronicles Series
(UK first publication dates, unless otherwise specified)
Beyond the Deepwoods (1998)
Stormchaser (1999)
Midnight over Sanctaphrax (2000)
The Curse of the Gloamglozer (2001)
The Last of the Sky Pirates (2002)
Vox (2003)
Freeglader (2004, USA Feb 2006)
Winter Knights (2005, not yet in US)
Clash of the Sky Galleons (UK Oct 2006)
The Stone Pilot (2006 - an 80 page story produced exclusively for the charity "World Book Day" in the UK)

The Far Flung Adventures Series
(UK first publication dates, unless otherwise specified)
Fergus Crane (2004)
Corby Flood (2005, USA 2006)
Hugo Pepper (2006, USA Feb 2007)