This is a review of both 'Clannad' and 'Clannad Afterstory', if your wondering.
Story: Based on the visual novel of the same name, 'Clannad' tells the story of Tomoya Okazaki, a former basketball player who had been forced to quit his school team and all of basketball, and who's now going through life aimlessly. With him on this downward spiral is his 'friend' Sunohara, a former soccer player who had also been forced from his team, after he had attacked his coach; it's hard to tell what their relationship actually amounts to, though that'll be mentioned in a minute. Okazaki has to go up this hill to get to school; one day he meets this girl, who's standing along the path, who asks him if he'd go up it with her. This incident sparks a kind of chain-reaction. Okazaki develops a relationship with this mysteriously gentle Nagisa Furukawa, her family, others from his school and all of these girls who all, in normal harem fashion, fall in love with him.
Simple enough. Of course, the visual novel this is based after was developed by 'Key', and in true 'Key' fashion, the story doesn't end too happily, or begin happily, as a matter of fact. After a while, what little which has been established is fully revealed to us, like why Okazaki isn't playing basketball anymore or why Nagisa talks with him. It's not depressing. Sad maybe? It's ending isn't depressing either; it may even make you smile, while your crying manly tears (or maybe that's just me). That's not to say the story isn't fun either, in fact there's more of an emphasis on comedy than on romance, and for a harem, the humor's pretty smart. There are laugh-out-loud worthy scenes to be had, if your interested, and when I say Tomoya's living life aimlessly, I'm not saying he's moping. He's sad and depressed of course, but he manifests it by playing pranks on others; he mentally tortures Sunohara, in particular, and all with this sarcastic smile. Getting past that and going back to the romance and this whole emphasis on 'family', the whole production has this warm, genuine heart to it. Unlike with most other harem shows, this develops it's heroines (if only just enough) to all be likable instead of just setting up some caricatures to drool over. Okazaki himself defies how a male lead in a harem should be by not being a completely unlikable failure, and then comes when you try to decide the story's genre; there's romance and comedy, but then there's fantasy and tragedy thrown in, and then there's the drama-club plot that's been developing this whole time. It accumulates back to this being a very comfortable/nice show (in tone and story and it's production-style) to watch, which ought to get you emotionally involved, if only a little.
Production: The music score sounds like something from a visual novel (no shock there). The opening looks like something from one as well (maybe it's the same opening as the game's; I don't know). This was produced by Kyoto animation in between making 'Lucky Star' and 'K-ON!', and it shows; it tries looking like the visual novel and that works, and the actual animation is very fluent, like everything after Lucky Star, though not so much as K-ON!'s.
Conclusion: A sometimes visually breath-taking show with simple but engaging intertwining stories and characters, who could've been forgettable but who are handled by obviously talented writers (I mean, it was written by Key, the people who did 'Air', would did you expect?).