where the barriers between the fantasy and real worlds break down; and , set in a world where certain elements are seen as irrational by the reader but are unquestioned by the characters. In 2016 Mendlesohn wrote Children's Fantasy Literature: An Introduction with collaborator Michael Levy. The book traces the development of children's fantasy from the 16th to the 21st centuries, covering events such as the collection of folk tales, the impact of world wars, and the emergence of young adult fiction. It was the first work to blend the history of the fantasy and children's literature fields. Awards and nominations In 2005 Mendlesohn won the Hugo Award for Best Related Work for The Cambridge Companion to Science Fiction, which edited with historian Edward James. James and Mendlesohn also edited The Cambridge Companion to Fantasy Literature, released in 2012, and wrote A Short History of Fantasy in 2009. Mendlesohn's book Rhetorics of Fantasy won the BSFA award for best non-fiction book in 2009; the book was also nominated for Hugo and World Fantasy Awards. In 2010 Mendlesohn was nominated twice for the Best Related Work Hugo, for The Inter-Galactic Playground: A Critical Study of Children's and Teens' Science Fiction, and for On Joanna Russ. They received the Science Fiction Research Association's Clareson award for distinguished service in 2015. In 2017, they won the World Fantasy Special Award—Professional for Children's Fantasy Literature: An Introduction. Their critical biography of Robert Heinlein (see below) was nominated for the Best Related Work Hugo in 2020. It won the BSFA Award for non-fiction, making them the only writer besides Paul Kincaid to win this award twice. Science fiction conventions Mendlesohn is an active volunteer member of the administration for science fiction conventions. Among other events, they co-chaired ConCussion, the 2006 Eastercon, with Simon Bradshaw; and was director of program for Anticipation, the Montreal World Science Fiction Convention, in 2009; Mendlesohn was on the convention committee of Loncon 3, the 72nd World Science Fiction Convention, but resigned as a protest over the announcement that Jonathan Ross was to be master of ceremonies for the presentation of the Hugo Awards; Mendlesohn remained division head for the convention's exhibits hall. Heinlein study In 2017, Mendlesohn announced that a critical study of Robert Heinlein was to be published by the crowdfunding publisher Unbound. the pledges had exceeded the target by 18%. The book was published in 2019, under the