It's like he's apologizing for the quality of the cover art. "Wait, wait! Please just stick around, I promise it's much better than this cover implies. In fact, I'm pretty sure whatever the hell's going on here isn't even in the book."
This is definitely one of those movies where nearly all the funny parts were in the trailer. The rest of the movie has a few minor chuckles and not much more. If you're still really interested in it, I'd recommend waiting for it to come out on DVD or Streaming and renting it.
If you do end up seeing The Watch though, please tell us what you think.