With the custom permissions indicated in the attached image set on a shelf, I expected the behaviour to be:
Users can View + Users can Create new books + Users cannot update the shelf details + Users cannot delete the shelf
Instead, the Create permission does not appear to have any affect unless Update is also ticked. This in turn means I cannot let people contribute books to my shelf, without also allowing them to edit my Shelf details.

BookStack v21.04
With the custom permissions indicated in the attached image set on a shelf, I expected the behaviour to be:
Users can View + Users can Create new books + Users cannot update the shelf details + Users cannot delete the shelf
Instead, the Create permission does not appear to have any affect unless Update is also ticked. This in turn means I cannot let people contribute books to my shelf, without also allowing them to edit my Shelf details.
BookStack v21.04