The Book Receptacle is a block added by Mystcraft.
The Book Receptacle can only be placed on a Crystal, on any side except the bottom. If placed on a Crystal Portal frame, right-clicking it with a Descriptive Book or a Linking Book will open the portal. The book can be removed via right-click with an empty hand.
If using a Descriptive Book, a link must be established before it can be used on a Receptacle.