This is a tough book to read for a couple of reasons. First, it seems like ontology is a fairly large field, which means that an introductory text like this is forced to cover a broad array of topics in a shallow way. Second, and somewhat related, is that it seems like the more "important" topics and theories in ontology haven't floated to the top yet (unlike, say, an intro Greek philosophy class where you know you're gonna be talking a lot about Socrates), and as Effingham points out, there isn't even really an established method for even comparing theories in ontology.
A couple of reviewers have also pointed out that Effingham can get a little tedious with his cutesy examples, and I can see that.
But despite all of this, there's still lots of food for thought here. I enjoyed it and feel like I learned a lot.