Aria belongs to what I like to call "slice of life manga" - that is, it does not posess complicated plot, but rather follows a character and shows all the little things that happen to him/her during their days. So it is with Aria, which follows its main character, Akari. In a future Mars which has been terraformed into a planet with an earth-like environment but too much water, and renamed Aqua, Akari lives in Neo-Venezia, a recreation of earth's Venice. She is an apprentice gandolier, called undine in the world of Neo-Venezia. The manga has a slow, dreamlike pace. It shows all the little, wonderfull things that happen during our lives. You know the statement "life is what happens while we are busy doing other things"? Akari washes her gondola and notices that the spray from her hose forms a rainbow. She guides a grumpy old man on her boat through the beautiful canals of Neo-Venezia in autumn, leaves drifting gently from the trees. She meets an aquaintence and they both wait for their mutual friends on a bridge, and feed the ducks below. She goes on a trip to another island that has a japanese shrine on it and witnesses an unusual wedding.
The art is beautiful, full of joy and good at conveying the quiet (or sometimes raucus) beauty of the surroundings. The production of the manga is very good - the paper is of good quality, there is a color insert, the sound effects are in original Japanese with a subtitle in English below them. The translation seems good, without any "Americanisms", and there is a page of translator's notes in the back.
Overall, I liked this manga quite a bit. If you are looking for action, a fast moiving plot, or lots of emotional angst in your manga, this is not for you. But if you are the type that likes to stop and smell the roses, you will like this as well :)