I have also been buying up books about numismatics.
I'm mainly focused on Pre-33 gold but some of the books I'm looking for are out of print and the folks who have them want a nice chunk of change for them.
The ones that are in print still cost $30+ but its totally worth it. Lots of these books have full-color photos and great information on mintages and survival rates of some of the coins.
Thanks for posting about these sweet JM bars, looking forward to the next lesson...