Kasdan shares script credit with Leigh Brackett, but apparently her contribution to the final film was minimal – a contention borne out by subsequent scholarship on the Star Wars trilogy. Whatever else Kasdan accomplishes in his career, this is wonderful work, full of tough, slangy dialogue and genuine emotion.
The piece is unavoidably fragmented because it’s two stories – Leia and the gang fleeing from Darth Vader, and Luke being trained – but it's excellent. Apparently Kasdan got the gig partly because his script for Continental Divide had Howard Hawks-like dialogue; that flair is on display here, not just the Han-Leia stuff but also the banter involving Lando and C-3PO. And Yoda is perhaps the most memorable character in the whole trilogy. The story has genuinely clever twists: Han flying into the asteroid field, and attaching himself to garbage; Vader revealing his parentage to Luke (though why didn’t more people think he was lying?). Marvellous.