4.5 stars. The follow-up to Relic takes Agent Pentergast, Lieutenant D'Agosta, and Margo Green, museum curator, into the dark and uncharted territory of underground New York City, where a new creature (or creatures...) is wreaking havoc on the city. I loved the first two-thirds of the book. The pacing was great, and the descriptions of the vast tunnel system beneath New York City were fascinating. Unfortunately, the book got a bit chaotic in the last third. Too much description bogged down the climax, and there was so much going on that too little time was devoted to the protagonists themselves. But aside from that, I'm loving this series, and I look forward to reading more.