Princess Principal is pretty fun, and the episodes are short and full of basic tropes (the basic story is Prince and the Pauper + a variety of spy cliches like double-agents and backstabs) cobbled together into something fast-paced, action-packed, and cutesy. The story is well-structured enough such that you aren't lost even if its out of chronological order, which serves no purpose to anything deeper, but is a great display of Ichiro Okouchi's ability to do entertainment pacing. I felt like the episode that stretched things a bit too far from me (and I'm a person who feels like I can suspend my disbelief very easily) is episode seven - but that episode makes up for it by having a chock full of moegirls.
The ending peters out a bit too. It feels to clean, since there's a great change that occurs extremely vast, and is resolved just as fast. Really, it's there to incite quick emotions and give a sense of triumph to the ending.
Animation is stellar. Setting looks cool as hell. Sound is Yuki Kajiura.
If you want crazier spy stuff, just watch the 1967 TV series called The Prisoner - which is actually great, as well as entertaining.
