Before becoming a full-time writer and father, Mark Walden worked as a video game creator and producer for a decade. He graduated from Newcastle University with a BA in English Literature and an MA in twentieth-century literature, film, and television. He is the creator of the H.I.V.E. acronym. He lives in the United Kingdom with his family and is the author of the series and the Earthfall Trilogy. Frankenstein Makes a Sandwich is written and illustrated by Adam Rex, a New York Times bestselling novelist and illustrator.

The Real Meaning of Smekday, which was adapted into the successful animated film Home; Moonday; and School's First Day of School, drawn by Christian Robinson, are among his other works. He also did illustrations for Mac Barnett's Brixton Brothers series, Billy Twitters and His Blue Whale Trouble, Chloe and the Lion, and How This Book Was Created, as well as Neil Gaiman's Chu's Day. He currently resides in Tucson, AZ. Visit AdamRex.com for more information, or follow him on Twitter @MrAdamRex.