TMCC is so easy to operate with it's limited command availability, that aside from knowing about the dreaded "black signal hole caused by house wiring and tin hats" I don't know what an in-depth add-on manual would be of much value.
Thus far, knocking on wood here, we've not experienced 1/10th the problems with TMCC we have with DCS.
The DCS add-on information books/forums/etc are a lot of value.