We actually lied in that headline: Reese Witherspoon has signed on for a James L. Brooks comedy, but *How Do You Know? ***is only the working title, with a final moniker still to be fixed.
Not much has been revealed about the plot as yet, but we do know that it's an ensemble comedy with at least three major characters, of whom Witherspoon is the first to sign up. That puts this firmly in line with Brooks films like Broadcast News or Terms of Endearment, both of which also had similar set-ups.
It's James L. Brooks' first film as director since 2004's Spanglish, and he's also written the script. Shooting's due to start in March, with Witherspoon leaving in July for a Cameron Crowe romantic comedy. Watch this space for further casting announcements as we get them, or feel free to speculate wildly on the plot and title of the film below.