More like moderately successful, which is what Lucas once said he thought was going to happen. If SW had really bombed, nobody was going to want to see another one. It's interesting to look at it now, in light of how it was designed to make use of leftover props and costumes, and the fact Harrison Ford wasn't signed up for any sequels.

I have wondered if any pre-production art or storyboards were ever done?

Both books are well worth reading, and are as close to vintage unfiltered Star Wars as you can get these days. That, and the Brian Daley Han Solo books.