The story follows Tomoya Okazaki, our standard high school student. Except that he hates his life, which I'm fairly certain most of us don't. Tomoya's character is somewhat shrouded in mystery at the beginning. We don't see immediately why he acts as he does. It makes the reveal all the more hard-hitting when we do see it, and we understand that Tomoya isn't just your standard harem protagonist. He's got his own issues to work out as well.
Now, on to the heroines. The main heroine is Nagisa Furukawa, a rather shy girl with some cute little antennae on her head and a lot of confidence issues. There is, or at least used to be, a lot of flak regarding Nagisa. Personally, I enjoyed her antics and her character. I found her overwhelming sincerity and naivete to be rather endearing, and she does start to go through quite a bit of development over the series.
Two of the other four heroines get their own story arcs within the series, Fuko Ibuki and Kotomi Ichinose.
Fuko is a freshman who's hiding a little secret along with a metric ton of wooden starfish(yes, they are starfish). Her story arc focuses on an event that is of utmost importance to Fuko. Sadly, I felt that Fuko's arc had the least emotional impact of the three arcs covered in the series. It just didn't hit me as hard as the other two did, and I'm not entirely sure of the reason why. It certainly did hit me and the arc ending was bittersweet, but for me it had just a little less emotional punch than the others, which is a shame, but by no means did I not enjoy it. The best part about Fuko is her daily antics. She's a damn good laugh, and so is at least half of her story arc, and for me that's the strongest part of her story. It's a good thing too, because Fuko's arc is first in line, with Kotomi's and Nagisa's following in that order and they hit pretty hard.
Kotomi is, rather bluntly put, a frigging genius. She's academically perfect, spends all her time in the library reading, never has to go to class and still aces all her exams. I'm sure all college and high school students everywhere wish they could do that. Unfortunately, like all the other heroines of Clannad, Kotomi has serious emotional issues of her own that Tomoya has to help her resolve(because, y'know, that's how he gets his harem). The thing I liked best about Kotomi's arc was how suddenly it hit you with "the feels". Unless you've been spoiled, most viewers aren't likely to see it coming, which is nice because emotions have their biggest impact when they arrive without any advance warning. The resolution of Kotomi's arc is also pretty emotional, except on the other end of the spectrum, which provides a nice contrast with the events before then.
The other two heroines, Kyou Fujibayashi and Tomoyo Sakagami, are also pretty important characters and have a big impact on the storyline but their own story arcs are reserved for the two OVAs, Another World: Kyou Arc and Another World: Tomoyo Arc, so if you're hoping to see the focus on either of them, I highly suggest that you watch the OVAs.
Overall, the part that I enjoyed most about the characters is that they all feel very real. I got the sense that they were real, that the emotions they felt were real. I could smile and laugh with them, cry with them, and love with them, and that was something truly special that I can say only about a very few shows.
The art style is firmly fixed in "bishoujo" style, which may or may not be a good thing depending on your tastes. I didn't really put too much stock in judging the series based on its art style, but I think the art fits the general feel of the series relatively well. You might come across a couple instances of generic cuteness or something similar, though.
A lot of the soundtrack comes from the original Clannad Visual Novel. The opening and ending, Mag Mell and Dango Daikazoku respectively, set the tone of the series very well and get you in the mood for the emotional roller coaster. One other notable piece, titled "Over", is used in Episode 18 and carried a lot of impact, especially once you read through the lyrics, and is in my opinion one of the best-placed pieces that the original series has to offer. A lot of the other BGM aren't masterpieces, as you might expect, but they do fit the scenes that they're used in relatively well.
I enjoyed Clannad very much for a wide variety of reasons. As I mentioned before, the characters were a large part of it. Watching characters that could be a neighbor, or a friend, or even a simply acquaintance gets me immersed and invested in the experience.
The other big part was the aforementioned emotional roller coaster that Clannad is well-known for. I've heard it said that Clannad is one of those shows that can make you laugh and cry both in succession and at the same time, and I feel that description fits the show perfectly. It took me quite a while to finish the 23 episodes that make up the original Clannad series, but at the end, it felt almost like a cathartic experience.
Clannad is a solid and enjoyable show if you enjoy slice of life antics, romance, and emotional punch. The story arcs might throw some people off and it is a little slow at first, but once the roller coaster starts, it rarely ever stops. The characters are definitely the best part about this anime, though. Every single one of them has flaws and emotional baggage that each one has to deal with, just like many of us in the real world. A big theme that has so far gone unmentioned in this review comes into play here: the concept of a family. Clannad tells us that family doesn't have to be related by blood. A family is made of those who wouldn't turn their backs on you or kick you when you're down. They would put you over their shoulder and get you to stand back up again no matter what life throws at you. A family supports each other not just physically, but also emotionally, no matter what might come between them, and if the only thing anyone takes away from Clannad is that, then the show has accomplished much more than anyone could have ever expected.
