There are bugs with items dropped by adventurers into retired fortresses. They don't seem to affect simple items like bars of metal, only complex manufactured items like artifacts, armor, and weapons.
No guarantees with these bugs, but I would try:
1. Double-check to make sure that the book isn't forbidden. With books and other artifacts, it's not obvious when an object is forbidden.
2. Run this script while there aren't any merchants on the map. It scrubs the foreign and trader flags off every item in the fort.
for i, item in ipairs (df.global.world.items.all) do
if item.flags.trader then
item.flags.trader = false
dfhack.println ("Trader Flag Unset")
end
if item.flags.foreign then
item.flags.foreign = false
dfhack.println ("Foreign Flag Unset")
end
end
3. Put the book onto a pedestal, then destroy the pedestal. If that doesn't work, put it on a pedestal and then remove it from the pedestal.