As I have posted in other threads, I believe very strongly in reference material, but the best is usually very expensive. I have several wonderful auction catalogs that have great illustrations, photos, researched descriptions and comments, and prices realized. I generally buy certain auction house catalogs off of the internet, but the prices have climbed there also. I forgot about this resource and thought I would bring it up
Spinks has produced many auctions catalogs
There are 26 stamp related catalog for 2007-2008
14 for 2006
and 11 for 2005
They are in .pdf format for the Free Adobe Acrobat reader most computers probably already have. Some are 10 MB, but I think you will enjoy them. Right click on the illustration and I choose open in new tab and it downloads. Most are on Brittain or related ( Australian!)
The first one for 2007-2008 is on the Monarch Collection. Very nice !
http://www.spink.com/auctions/pdf/default.aspJim