Length: 6 graphic novels, 49 anime episodes (20/29)
Experience (a.k.a. how much I've seen to base the review on): All of it, the anime first.
Genre: Fantasy with elements of magical girl and giant mecha. On the darker side for one of the cute CLAMP series.
Plot: Three girls who have never met, but happen to be at Tokyo Tower on field trips at the same time, are drawn into the fantasy world of Cephiro, which is in need of their help. The Pillar, the woman whose prayers sustain the world's existence, has been captured, and three girls from another world (and therefore not hampered by the properties of Cephiro) must become the Magic Knights to save her. This involves questing for mystical weapons and armor as well as the aid of the three Rune-Gods, and the inner struggle to master the magic that they've been granted. After their quest's dramatic conclusion, they return to Earth, only to be called to Cephiro once again as their previous adventure left Cephiro vulnerable, and the three surrounding "countries" (they're more like planets, as space travel is the only way to move between them) are moving in to conquer Cephiro and capture the power of the Pillar for their own purposes.
My opinion: This, not surprisingly, is the groundbreaking work that put CLAMP on the map, probably back when they were still a 20-something strong team rather than the four women who now work under the name. And in the tradition of my own earliest stories, you can see how much their storytelling has improved over time. Had I read the manga before I watched the anime, I probably would have sworn off CLAMP forever, Cardcaptor Sakura aside. It's not really BAD... the first half of the manga is quite good, and as I implied above, the ending of the first half is better than most endings I read. Had they ended the story there, I'd have loved it through and through. Then they wrote MKR2... the sequel that screams "They'll pay for more pages." There are three countries trying to invade Cephiro, but when it comes down to a one-on-one with the invaders from Autozam, the other two countries are pretty much ignored. I couldn't see any reason for them to be there, because they never really DID anything. They just stopped being in the story. And the end of THAT part... right out of Dr. Seuss, I swear. Go to the bookstore, pick up MKR book 6, and just turn to the last page of the story and you'll see what I mean. I promise you won't be spoiling any of the good parts.
Now for the anime. The anime, naturally, has much more story to it, and a good deal of it is filler. But in the usual tradition of CLAMP anime adaptations (Chobits notwithstanding... and Angelic Layer is pretty hit-or-miss), the filler is better than the original material and really rounds out the story. There's actual, honest character development, much more drama, some random monster encounters that relieve the story of its original rushed pace, bad guys worth being interested in... and that's just the first half. The second half introduces a completely new villain as well as giving those two sidelined villains something to do, even if it is completely tangential to the main plot. It's three-on-three instead of one-on-one. In a manner of speaking, that is... each of the three encounters between a Magic Knight and an invader is separate, but they build all of the story threads to a generally satisfying conclusion. It gets a bit slow around that point, because no thread is really going anywhere at any time, but it all works out by the end. And there's a lot more romance going on.
It does have the feel of a children's show at first, so I'm sure the Ninja Scroll fans will stop watching long before they reach the second, darker season. But as Hikaru points out in the first season, it feels like an RPG. Level-ups, weapon and armor upgrades, new spells, the giant robots... it's all there, without the HP meters. The second season abandons that feel in favor of a deeper story, the ending of which you'll see coming a mile away (especially if, like me, you make the mistake of watching the Outtakes on the third disc, most of which are from the seventh disc, before finishing the series). But I enjoyed it, and it was only the second CLAMP series I'd seen (after some of Cardcaptor Sakura), so I wasn't the fan I am today. I'd skip the manga and watch the anime. If nothing else, you'll get to see Primera the fairy in all her comic relief glory.
Also, very big credit to the second season for its opening theme... my favorite anime song of all. I absolutely love that song.
If you want to add something or request a series for a future review, comments are welcome. Also let me know if the format works or if you'd like to suggest an improvement. It's not set in stone yet.