Under the current system there is no way for a level 20+ character to find out which heroic tome of learning he has used (if any). The same applies to a TRd character below level 20 and epic tomes of learning.
Additionally, a TRd character at low levels cannot tell which stat tomes they have used, as they re-apply gradually when the character levels up, and only the current "plus" is visible, but not the actual "size" of the tome.
It would be nice if full tome information were provided on mouse-over. For example it would be nice if a level eight TR character who checks his tome of learning sees something like "Greater Heroic Tome of Learning (Lesser Epic Tome of Learning)", and his ability tome bonuses would be shown as "tome +2 (+4)", with +2 being the currently applied bonus and +4 being the full bonus that the tome will eventually provide.