Yes i'm going to focus mainly on the Anime but honestly.... all CLAMP Anime follows extremely close to it's manga counterpart.
So Magic Knight Rayearth is pretty easy explain. there are a bunch of school who have gone to Tokyo tower for a field trip and there is a bright light... suddenly one girl from each of the three schools gets teleported to the land of Cephiro.
They see the large ocean, a floating island and a large volcano in the distance as they hurtle through the sky towards their death.... luckily a giant flying fish saves them.
they meet a very small man in a very funny outfit named Clef and he explains that Cephiro is a land controlled by ones will, he then teaches them magic and explains they need to save the pillar of this world and grant her wish before they can return to Tokyo.
To be able to grant the princess' wish they need first get weapons made of a certain material that will evolve as they get stronger and then they need to find the Rune gods to be able to fight off the high priest Zagato.... then clef gets turned into stone and the girls have to navigate this foreign world on their own.
they meet friends and some characters even die and eventually they get the weapons and the rune gods and they defeat Zegato before they find out that he is not the final Boss...the princess is... see she's tired of praying for the world and wants to be with Zegato but will only be able to be with him in death...
oh yeah totally a happy fun time magical girl story.... ok.... where to start.
Despite seeming like your typical magic girl show it has some fairly dark themes, characters die for good (... well... at least in this season... i'll get into that later) others get injured and bleed.... and in the end even though your just trying to complete your mission of granting the wish of the pillar of this world you have to soil your hands with the blood of someone who has done you no wrong
Also, even thought Hikaru is technically seen as the leader of the group there is no real leader.... by that i mean in shows like sailor moon when new powers are given it tends to go...
Sailor moon>Mercury>Mars>Jupiter>nevus.... almost always this order.... slight variations randomly but nothing major.
In MKR it's random... each of them have a chance at being the one to learn the skill first or get the first rune god.... you don't see this a lot in magical girl anime so yeah.... bonus.
The character design is really good, extremely colourful and just pretty to look at... i believe (i'm probably wrong) MKR was their breakout hit that put CLAMP on the map... and it's easy to see why, the story is well done and the characters are likable....
The not so good:
Mokona.... i don't like this thing only because it feels a little cheap when that go "oh we need this" then Mokona pops in and goes "Puu Puu~" and magically they now have what they need. it's just way too easy and honestly it doesn't add to the plot at all (well.... in the first season at least....)
the animation, epecially for filler episodes, is not the best.... this is in part because of clamps style not easily translating from Manga to Anime... but it's better then macross which is a plus.
Forgettable.... i've read the manga and watched the show 2 or three times now... and i still barely remember whats going to happen next... it's just this blank void in my mind.... don't know why.
The dvd.... I have the media blaster dvd release which just plays the english right when you pop it in.... so i have to hear a few seconds of that terrible english dubbed intro while i hunt for the remote to get to the Japanese settings...
so yeah it's not a bad show but it's not my favorite CLAMP adaptation.... no that will forever be held by Cardcaptor Sakura... but that's for another time.