Wayward son is kind of a shit sequal. 

The bigges issue is that the original appeal of this series is a) the fun magical world that doesn't take itself too seriously and b) Baz' and Simon's relationship. This sequel doesn't give us enough of either. 

Instead, Wayward Son feels like patting between book one and book three. I enjoy the discussion of the fallout on everyone's (mental) health and the relationship troubles of Simon and Baz, but Rainbow: where's the plot, love? There isn't any! And the book takes forever to get to the sliver of plot it has. It's very unsatisfying and makes that I don't really want to read the third book (even if I'll probably try because 'in for a penny, in for a pound').