 Since the films had been released some years previously, and there was (at the time) no new media forthcoming, the success of these books came as a surprise.The game established much of the groundwork of what later became the "Star Wars" expanded universe.Lucasfilm considered their sourcebooks so authoritative that when Timothy Zahn was hired to write what became the Thrawn trilogy, he was sent a box of West End Games Star Wars books and directed to utilize the background material presented within.