After nearly three hundred years of deliberation, Double Falsehood has been included in the latest Arden Edition of the Shakespeare canon, which was published last month. This lost play, first published in 1727, has always claimed to be a reworking of a 1613 play written by Shakespeare and John Fletcher, but from the first, Bard watchers have been skeptical. Double Falsehood was clearly not 100% Shakespeare, after all. Even Brean Hammond, the Shakespearean scholar who spent 10 years studying the play and editor of the Arden Shakespeare Edition, believes that the 18th century publisher of the play, Theobald, significantly "cut and altered the work to suit his 18th century audience" though in an interview with the BBC, he says he is certain that Shakespeare "had a strong hand in" the first act, the second act, and at least part of Act III.
The 17th-century stage was somewhat collaborative, but should anything outside of the 1623 First Folio count as canon? Arden and Hammond voted yes, and a reignited interest in Shakespeare is the result.
A representative from Bloomsbury, who publishes the Arden Shakespeare series, says "the Arden General Editors and Arden publisher, Margaret Bartley, took considerable risk in publishing this title because they believed it was in the best interest of Shakespeare scholarship. It was a bold move but true to Arden’s roots as the pre-eminent publisher of Shakespeare and early modern drama studies for more than a century."
Decide for yourself: The Guardian has a short excerpt. I haven't read Shakespeare since college so my opinion means exactly less than zilch, but I have to say I'm curious.