As has been noted, this is an incredibly detailed account of the 1944 Ringling fire. I've been reading a lot of historic fire accounts recently (Coconut Grove, Triangle Factory), a lineup that has to include the story of dozens of happy children who burned to death at the circus.
The one thing that truly sets this book apart from the others is the way it's told. The normal style is to open with the fire, follow it up to the height of drama, and then step back in time (decades if necessary) to tell the entire history of everyone involved before finishing the fire events and continuing on with the aftermath.
Circus Fire, on the other hand, tells a totally linear story, from the Cleveland fire to the setup in Hartford and on to the present day, in order. It's a refreshing change from the manipulative emotional rollercoaster style of most dramatic nonfiction. Personally, I appreciated the respect that shows for the reader's intelligence.