I have looted the Zhar’doom Greatstaff of the Devourer, I have transmogged it to my current weapon. Entered Antorus and killed the Portal Keeper, took the fire portal and found the proper gate. When selecting the gate I chose “Channel the power of your weapon into the gateway”, and begin to channel my weapon. The animation happens, the book appears at the end of the cast then BOTH the BOOK AND PORTAL disappear completely.
Correction: You now auto loot the item, however it is giving the character 5 copies of the same book for some reason.