Richard Bachman
In 1996, Bachman's The Regulators came out, with the publishers saying the book's manuscript was found among Bachman's leftover papers by his widow. It was released as a companion novel with King's Desperation; the two novels took place in different universes but featured many of the same characters. The two book covers were designed to be placed together to form a single picture. In the foreword by King included with Desperation he said that there may be another Bachman novel left to be "found."