This is NOT a bug.
You’re in the wrong room, clicking on the Scribe’s Lectern. The “Pages” you’re picking up are parts of a Journal. Each part only drops once. They don’t go in your Inventory. They initiate a dialog. Once you have them all, the Lectern only drops Gold.
You need to be in the “Library” room in the Royal Quarters and click on the Tome of Set Dungeons.
Edit: Just for extra clarity:
