He was born in Gods Lake Narrows, Manitoba, where his father served as minister in the United Church of Canada.
In March 2010, Thornton visited the EuroMedic clinic in Katowice, Poland, to become one of the first Canadians treated for CCSVI, a vascular problem common in MS patients first described by Dr. Paolo Zamboni.
His first novel, Kalifax [1] (1999), a young adult fiction fantasy described as a fairy-tale retelling of the search for the Northwest Passage, was nominated for the 2000 Governor General's Award for Children's Literature.
The sequel, Captain Jenny and the Sea of Wonders [2] (2001) was a counterpart inspired by classic literature of Old World exploration.
Thornton was the founding editor of the electronic version of Canadian Materials, one of the first regular on-line publications in Canada.