It is great to know that you like it Alex.

Literature? I think Christopher James wrote a great book: The Book of Alternative Photographic Processes, Second edition, and half an hour ago I ordered The Keepers of Light: A History and Working Guide to Early Photographic Processes by William Crawford. I do not know about books specific to the kallitype, but there are also many resources on the wire e.g. Alternative Photography would be a good start. And of course there should also be some info on APUG.