This is something our group has struggled with now and then because this isn't really handled in any of the core books. I like the match ups between monster type and skill and I really like the table that describes how having a better success on the skill check gives more information. On the other hand, I think the class affinity seem a little forced. Almost as if they were trying to find something for every class to be good at. Our group is more likely to grant the affinity bonus more on whether the individual character can justify it... for example, a fey patron warlock has good reason to know more about fey.
All in all though, it's a far better approach to the issue than what is currently in the core books.
[4 of 5 Stars!]