I have always been interested in this campaign after reading 'The Gardeners of Salonika' by Alan Palmer, sadly long out of print. I have collected a fair number of books and there is an excellent Salonika Campaign Society with its journal The New Mosquito. For an introduction I would recommend Under the Devil's Eye by Alan Wakefield, published by Sutton in 2004.
I had dabbled a bit with this campaign in 15mm, but Warhammer Historical The Great War rules got me started in 28mm. I picked up some Germans, Turks and British at a bring and buy before getting stuck in seriously with the Greeks, Italians and Russians that I purchased in the USA at Historicon. Still some more work to do on these before doing something about the Tiger Miniatures Bulgarians gathering dust in the pending box.
In the meantime a nice German command base.