After getting a BA in English Lit at the University of Colorado, Lewis initially worked at a proofreader at the University of Arizona Press in Tucson, then spent about six months teaching English in Barcelona. After that, he earned an MA in teaching English to speakers of other languages, then taught at a US university and then a manufacturing company in Japan. In 1995, Lewis took an editorial job with an international publisher in Hong Kong, and in 1997 became a freelance editor, project manager and writer in the UK. He now writes full time. Lewis has worked on books, videos, tests, audio materials, worksheets, apps and online materials for learners of all ages across the world.