Someone brought this back from the SHA's in York:
Ayto, Eric G.
2002 Clay Tobacco Pipes. 3rd edition. Shire publication, ltd. www.shirebooks.co.uk
This short book has a good description of pipe making and a little about figurines, but not much interpretation on figures.
http://www.claypipes.com/UK.htm
Canadian Clay Tobacco Pipe Industry:
http://www.virtlogic.ca/pipe/pipes.html