Reese Witherspoon is heading into uncharted territory. At Hello Sunshine's Second Annual Shine Away Conference, the Big Little Lies actress, 48, tells PEOPLE about how her upcoming novel that she's co-writing with Harlan Coben is different than anything she's done before.

Sevier brokered the North American rights deal with Cait Hoyt at CAA for Witherspoon and Lisa Erbach Vance at the Aaron M. Priest Literary Agency for Coben. Century, a division of Penguin Random House UK, will publish simultaneously in the U.K. and Commonwealth (excluding Canada).

Reese Witherspoon is writing her debut novel. The “Legally Blonde” actress recently teased that she had a new project on the horizon and she has now revealed on social media that she is co-writing a thriller with “Fool Me Once” author Harlan Coben - who has had a number of his 35 novels turned into popular TV shows - which will be published by Grand Central Publishing.