No you're not missing anything. It is indeed single action. The M&P22 is very different compared to it's bigger brothers. But they designed it to be that way. If you're really considering it, you're not making a bad choice. As far as 22's go it's a solid pick. Very dependable, easy to shoot, and super easy to maintain. If you're looking for information there is a ton all over the web but here are the basics:
12+1 version and a 10+1 version
24 oz. weight
manufactured by Walther in Germany
Hope that helps.