That's still sage advice. Cash the check and don't look back. Above all, don't read the screenplay they send you. That's what put Barry Longyear (Enemy Mine) in the I.C.U. with a massive coronary.
If the movie credits only say "based on a novel by Joe Blow", you can't be held responsible for their butchery.
That's why, as you say, you should not read the screenplay.
What counts is the number of zeros on the check.