My 15 year old read Catch 22 this past summer and loved it. I read it years ago and loved it, then read it again after my son and thought "Oops, it's a bit more adult than I remembered!" Still very funny though.
It does pick up. Don't give up until you've given at least the first couple of hundred pages a go.
Catcher In The Rye falls into place at the bit where he says he's like a catcher in the rye, and you finally understand what the book is about, and what the title means.
In my opinion, Catch 22 is quite an exceptional book. I couldn't get into it at all, so after the first couple of dozen pages I stopped, and started again. This time I got the hang of it and thought it an extaordinarily funny book. Read it again, and was left with the impression that it was rather more serious than I'd first thought. Read it for a third time, and concluded that it has to be one of the most damning anti-war books I've ever come across.