Piers Anthony's books pretty much always have some very... interesting (not really)... views on anything to do with male-female relationships. Across a representative variety of
types of relationships.
The main character of his Xanth series married a girl who is sometimes beautiful and dumb, and sometimes smart and ugly.
Apparently the variety is a desirable thing, because no one wants to have sex with smart people.
This is supposedly suitable for children to read...