I was messing around with the latest snapshot and put a written book in the relatively new Lectern. Naturally, I wanted to break the lectern, and it dropped the book. Exactly as I thought. Then, I went to pick up the book, and noticed that instead of going to a separate slot, like would happen if two identical originals were in the inventory would, the book stacked with the one that I put in originally.

I don't know if this is a guaranteed bug, or if it's actually that the books aren't stacking and they should, but I thought I'd report this anyway.