How to create a book link to a card?
There are cases where you would like to have links for common rules, like conditions, but that aren’t included in our base Shard capabilities. There is a way to do this yourself for things that we haven't done. Custom types can be resolved just like other objects. You can create custom types and then resolve the names to those types. This technique was used in Cthulhu Mythos since it has many of its own concepts. In there a custom type called Reference Cards was used.
To create your own go to My Creations and click NEW CUSTOM.
After you create the reference card you can then use that text in books or other rich text to create links to the card.