Your wrote and reviewed examples sounds like two binary fact types: Person wrote Book; Person reviewed Book. There would be a pair-exclusion constraint between these fact types, so no person can write and review the same book. In this case, each argument of the exclusion constraint is a (Person, Book) role pair.
An exclusive-or constraint can apply only between single roles, not role pairs. It is a combination of an inclusive-or constraint between single roles and an exclusion constraint between those same roles.
As a very simple example, each person is either male or female. You could model this with two unary fact types (Person is male; Person is female) with an exclusive-or constraint between the two roles. Consider the population
Terry is male.
Norma is female.
If you mapped this to a relational table under the closed world assumption you would get
Person (name, isMale, isFemale)
Terry true false
Norma false true
The exclusion constraint within the exclusive-or constraint ensures that we can't assert a person to be both male and female, so the following row would not be allowed
Fred true true
Hope this helps
Terry