It seems the Steinbeck loved the legends of the Knights of the Round Table. Read them as a nine year old boy and attempted to rewrite the Mallory version so as to make it more palatable to the modern (read as: late 1950s) nine year old boy.
I have a hard time with Arthurian legend, both because of the portrayal of women and the fact that it all ends badly.
I spent most of the book rolling my eyes and thanking Marion Zimmer Bradley for writing the totally necessary The Mists of Avalon to combat the horrific misogyny of Mallory.
Steinbeck didn't clean up any of that.
Seriously. With the exception of Lyne, the Old Maid that trains the heck out of Ewaine, every woman is stupid, helpless, evil or some combination of the three. The archetypal virgins and whores are rampant.
Here is something interesting. Steinbeck put the project down and didn't pick it back up. The last scene that he wrote was the first time that Lancelot kissed Guinevere. No tragic affair. No Holy Grail. No return of Mordred. It made me wonder if perhaps Steinbeck also had trouble with the it all ends badly.
Steinbeck's language does, in fact, make these tales easier to read. I still have a hard time with Arthurian legend.