It's as if he had so many fun ideas he wanted to explore that he just threw them all in this book in one last-ditch effort to use them all up. There is the Asgard subplot which made little sense. There was the harbinger of justice pitted against the embodiment of insanity that never went anywhere. It felt like the author was afraid he'd never get another chance to write another book and wanted to use every idea in this one without really considering how they fit into the larger whole. Because of that, the book stalled for most of its length and then torpedoed to the end at such a breakneck pace that I lost track of who did what and where. The confrontation with the big bad was anticlimactic and the ending was not nearly as surprising as he wanted it to be since I figured it out in the first book.
Don't get me wrong, this was still a lot of fun and I'm glad I read the series. I would recommend it to geeks everywhere with a high tolerance for a focus on world building over character development. Just don't expect any gender balance or depth. It is what it is, an exploration of what would it mean if dungeons were sentient and deliberately trying to kill you, but not too much. After all, if it kills everyone off no one is going to come back. Talk about exhausting your customer base.
3 1/2 stars for a fun, if uneven, ride.