Hi Jay & Pam-
I don't know of any books on the subject, but to clean my leather, I have always relied on Neatsfoot Oil to keep my saddles and leather cleaned and well conditioned.
For the rawhide headsets, I use Vaquero Rawhide Cream. It cleans and conditions, but does not leave any residue. It also helps soften new headsets to make the rawhide more pliable.