Whittall was born in 1976 in the Eastern Townships of Quebec and spent her childhood on a farm on the outskirts of South Durham. She graduated from Dawson College in Montreal in 1995, attended Concordia University from 1995 to 1997, and completed an MFA in Creative Writing from the University of Guelph in 2009. She works as a TV writer and previously worked as an arts reporter and in small press publishing. She lives in Toronto. Her first novel, Bottle Rocket Hearts, was named a Globe and Mail Best Book of the Year and one of the top ten essential Canadian novels of the decade by CBC's Canada Reads. She won the Writers' Trust of Canada's Dayne Ogilvie Grant for best gay emerging writer in 2008. She subsequently served on the award's 2011 jury, selecting Farzana Doctor as that year's winner. Holding Still for as Long as Possible, Whittall's second novel, was published in 2009 in Canada and 2010 in the United States. It has been optioned for film, and was shortlisted for the 2010 ReLit Award. It was an honour book for the American Library Association's Stonewall Book Award in 2011, as well as winning a Lambda Literary Award. In 2010 she published a short novella for Orca Books' Rapid Reads series called The Middle Ground, a book for adults with low literacy skills. Her poetry books include The Best Ten Minutes of Your Life, The Emily Valentine Poems and Precordial Thump. She edited the short fiction anthology Geeks, Misfits & Outlaws in 2003. In 2016, her novel The Best Kind of People was published in Canada by House of Anansi and shortlisted for the Scotiabank Giller Prize. In 2017, it was published in hardcover in the U.K. by Hodder & Stoughton, and in the United States by Ballantine Books, an imprint of Penguin Random House. The novel is currently being adapted for feature film by director Sarah Polley. The Best Kind of People was named Indigo's #1 Book of 2016, and a best book of the year by Walrus Magazine, The Globe & Mail, Toronto Life, and The National Post. Her forthcoming novel is called The Spectacular, and will be published by HarperCollins Canada and Penguin Random House U.S. in 2019. In 2018, Whittall won a Canadian Screen Award for Best Writing in a Variety or Sketch Comedy Series for Baroness von Sketch Show, alongside Aurora Browne, Meredith MacNeill, Carolyn Taylor, Jennifer Whalen, Jennifer Goodhue, Monica Heisey and Mae Martin. Whittall forwarded stories Djamila Ibrahim wrote for a creative writing course Whittall was teaching to Janice Zawerbny, her editor at the House of Anansi, and her publisher subsequently published Ibrahim's stories.
