Note: Some minor spoilers. Beware.

The summary on MAL is a little confusing so I'll try my best to make a more coherent one.

In middle school, there was a certain basketball team whose players had immense talent. This caused them to be dubbed the "Generation of Miracles". After finishing middle school, they all went their seperate ways but talk remained of a mystery 'phantom player', their 6th man.
The story starts with Kagami Taiga, a returning student joining the Seirin high school basketball team. Another person who joins is Tetsuya Kuroko. He's weak, can't shoot and has no presence on the court but herein lies his secret...

Story: 8/10
An interesting premise that is well executed too. It progresses nicely thus far and there's real development in both the plot and the characters. And it's nice to see a manga like this that isn't all victory and glory all the way, there's some real issues Seirin runs into along the way and watching them deal with these is interesting. There are some things I'd like explained sooner rather, such as the oath Akashi mentions at one point that was apparently made when they split up after middle school but up until this point has not been elaborated upon. But hey, ongoing manga so plenty of time to get that taken care of.

Characters: 9/10
Let's start off with the main character, Kuroko. He's quiet, always calm (to the point where I'm wondering if the author has been watching a few too many Christopher Walken movies), bad at basketball. However, his strong point is helping others by way of his completely and utter lack of presence on the court (something that quickly turns into a running gag off-court where his team mates will think they're alone until Kuroko actually says something). He's neutral but not boring. He's calm but not a pussy. Disliking Kuroko as a character is difficult because he always puts other people's needs ahead of his own.
Kagami (or to call him by my favorite nickname for any character ever, Bakagami) is the second main character and, as mentioned, a returning student from America. He's as blunt as a hammer, he is self-centered, he's a bit of an ass, so you could be forgiven for disliking him at first. But Kagami is a good example of character development in Kuroko no Basket. What starts off as a self-centered douche with all the subtlety of a brick to the face turns into a real team-player. He quickly finds Kuroko teaming up with him to help him and while he does so somewhat reluctantly, this helps him not only discover Kuroko's magic abilities but discover that teamwork can be far more efficient than going at it solo. He becomes more involved with his team mates and caring more about their individual skills and how they can help the team.
The side cast is a joy too. There's Riko, their second-year coach who has the magical ability to learn a player's skills and potential just by looking at their shirtless bodies (because what is shounen without some sort of absurd abilities), Hyuuga, the likable team captain and 3-point shooter and of course the rest of the Generation of Miracles.
They have distinct personalities, some of them funny and a joy to 'listen' to (Kise's fairly one-sided admiration of Kuroko never gets old), some of them a bit rotten (Aomine, looking at your general direction, just saying) and others are downright weird (Murasakibara, are you not secretly shizophrenic?) but they're all well-written characters.

Art: 8/10
Say what you like about KnB but it looks good. Characters look great with plenty of detail and the environments (and the courts in particular) are also easy on the eyes. The amount of sweat on the characters during matches did distract me a little bit at times but this is a sport manga so I'm going to call this a case of 'par for the course'.

Enjoyment: 9/10
186 chapters read and furiously awaiting the next one every week. Yep, sounds like enough enjoyment in my book!

Overall: 9/10
A solid sport manga with good story, interesting characters with development to go and a healthy dose of comedy mixed in. I'm calling this one a must-read for anyone interested in basketball or sports manga in general.

A miscellaneous note on KnB's portrayal of basketball:
I've heard some people call KnB over-the-top for its sometimes ridiculous display of matches (and reading chapters with matches against Aomine, I can definitely agree with that), making it too dumb to read. You have to take into account 2 things here. For starters, shounen targets kids aged 10+ so it just needs a lot of action to keep the attention of the target demographic. Second, and this is speaking as a basketball fan, having realistic depictions of basketball would be boring. KnB basically takes the best bits in basketball matches (fast attack, great defense, slam dunks, impressive plays) and throws out the rest and you know what? That's fine. I don't want to be flying through pages to get to the exciting bits, I want the exciting bits now! Preferably 5 minutes ago. Yes, it does get BEYOND over-the-top as mentioned before and you won't get arguments proving the opposite from me there. Kise's 1:1 copying of player's abilities, Midorima's ridiculous shooting range, Kuroko's vanishing and (the biggest offender in my book) Aomine's suspension-of-disbelief-butchering shooting, they're indeed over-the-top but they help keep everything fresh and original rather than every member simply being another good player to beat.