Kal,
The 2 books only spawn once every 8 days and seeing as there quite a few people that want the bookcases for thier libraries, etc. You will be hard
pressed to find them for sale for a long time, and if you do find them
for sale it will be for a pretty penny. Just between a friend and I
we need about 6 to 8. You figure the time frame

Best Bet, make a thief
and try to steal them before the ummm "others" do.
Or wait till the 11th collection comes out and I believe you will be able
to choose them. Not sure on the time frame on them.
Hope this answers all your questions on them.