Mij was born in Scotland but spent her early childhood in India. She studied English at York University, Publishing Studies at Stirling University and has had a host of different jobs – from tattie howking, cleaning and lexicography, to collecting oral histories, waitressing and journalism.
Her first children's book won the Kathleen Fidler award in 1993 and she's been writing ever since. She used to test out her stories on her children. Now she tests them on her granddaughter. She lives in York with her husband Dan and her dog Otis.