After nearly two decades, Mel Gibson is ready to bring the best-seller The Professor and the Madman to the big screen and has enlisted Sean Penn in the effort.

Gibson, who acquired the film rights to the Simon Winchester book back in 1998, is poised to star opposite Penn, who is in negotiations, in the true story of the creation of the Oxford English Dictionary — a tale that delves into madness, genius and two obsessive men who changed the course of literary history.

Though Gibson had long developed Professor and the Madman as a directing vehicle, he has handed the reins to his Apocalypto writer Farhad Safinia, who is set to direct the film. Gibson will play Professor James Murray, who in 1857 set about compiling the OED, one of the most ambitious projects ever undertaken. Penn will play Dr. W.C. Minor, who submitted more than 10,000 entries but also was an inmate at an asylum for the criminally insane.