I just finished reading these two graphic novels (I read at least part one of DKR a long time ago, but I don’t think I read the other 3 parts). DKR was a great book; it had a good story with Batman, Joker, Gordon, Superman, and a new Robin. It was a nice way to show Batman’s “last story.” The art was different, but good.
DKSA, on the other hand, was not as good. I did not like the art, a lot of pages were huge drawings (nice) or very cluttered (no so good). I did not like how the story focused on the whole world as opposed to just Gotham. We had only a cameo of Gordon, but we had lots of cursing and trashy pictures like “Nude on the News” which served no real purpose. I thought there was too much noise distracting from a decent story. And when the Joker-want-to-be’s identity was revealed, that pretty much ruined it for me. Even the ending came abruptly and was not as neat and tidy as DKR.
In my opinion, enjoy Dark Knight Returns, but skip the sequel unless you must have every Frank Miller or Batman book.