Though I should have done this at book 6 or 7, I will do it now. A halfway point review since volume 12 is so far the last one.
This series is absolutely wonderful, the art is top-notch, especially in regards of the background. You can just imagine yourself there, together with all the characters and enjoying your time with them.
So far the volumes have been set in the Summer, though we are now more in Fall and going to Winter. I really like that it is a slow speed, that we don't hurry through the seasons or months, but that all kinds of events are mentioned, festivals are done, beaches are visited and more. Now it is Fall, the leaves are falling, Yotsuba is searching for acorns, clothes are being bought for colder times.
And then we have the characters. I can say, that it took a bit of time to get used to Yotsuba, but around volume 2 or 3 I start to really like her, she is a wonderful kid, who really enjoys life. And not only the big things, no no, also the small things, like acorns or milk or newspapers. She is so enthusiastic about everything, you can't help but cheer for her, and also laugh at her antics.
Her dad, well he is a bit silly and at first I thought he wouldn't be a too good of a dad, but he is quite strict at times. When Yotsuba does something not good (running away, going outside, bicycling without anyone) he will give her a fitting punishment or tell her it is bad. He also learns her various things and takes care of her so well.
The 3 sisters and their mother bring a lot of fun, but also help with Yotsuba and take care of her.
Jumbo, the big friend of Yotsuba and her dad, is a really weird, sometimes childish, but also very kind and very generous and will do anything for Yotsuba.
Then we get to the only character so far that I absolutely hate and wish wasn't around. Yanda. He is obnoxious, childish, annoying and in overall I think he is just a bully and rude. He just walks into the house, while Yotsuba clearly doesn't want it (even when she was alone, which I think is strange of him to do so, because at that time she didn't knew him). Every time he is in the story I just want to skip over the parts. I can't imagine ever liking him, unless something major happens.
But all in all, it is a wonderful manga, and I would really recommend it. Be prepared to laugh a lot, cheer for various characters and more.