Sudbury: Rail Town to Regional Capital edited by C.M. Wallace and Ashley Thomson. The standard one-volume history of the city, covering the mining boom, the 1958 strike, the regreening, and the shift to a service economy. Academic but readable, and the best single source on how Sudbury became Sudbury.
Up Ghost River by Edmund Metatawabin. A memoir by a Cree leader who survived the St. Anne's residential school in northern Ontario. Not specifically about Sudbury, but essential context for the Indigenous history of the region that Sudbury treats poorly even by Canadian standards.
The Lost World of the Old Ones by David Roberts. Not Sudbury — but the framing of geology and human attempts to read landscape that Roberts brings to the Anasazi Southwest is the right preparation for understanding the meteorite impact, the Canadian Shield, and the strange burnt rock around the smelters.
Indian Horse by Richard Wagamese. A devastating novel about an Ojibwe boy whose talent for hockey takes him through the residential school system and into the lower reaches of the OHL. Reads like Northern Ontario itself.