Club 9 is an older manga series which can be quite hard to find now. I was first introduced to it through a book from the library on the artistic merits of Manga. Club 9 was given as an example of a very original manga, something unique and not really seen anywhere else.
The artwork is what stood out to me most. The characters are all drawn in a sort of hyper-deformed style which can take some getting used to. I think of it as being similar to the artwork of political cartoonists as the exaggerations play on some facial quality and often back up the character at hand. This really helps to avoid the "all characters look alike" problem. Other manga such as XXX Holic
also use character designs which are strangely deformed in a non-chibi way but Club 9's character design can take getting used to. As I mentioned, the character designs are reminiscent of political cartooning or maybe of Tenniel's art for Lewis Carrol in which characters were often drawn "deformed" for effect.
The second major quality I noticed is the language. The English translation is written to show the use of the Akita dialect in the original Japanese. The Dark Horse translators chose to portray this language with a very over-the-top Lil' Abner style language full of heavy "country hic" drawl. If you are unused to reading such heavy dialect such as might appear in Mark Twain novels, it can take some getting used to. For myself, it added to the humor as I have been around people who spoke similar to the accent portrayed (albeit the one in club 9 is quite stereotypically exaggerated) but this allowed me to be able to "hear" the characters talk in my head with fewer distraction. The use of this language is not throwaway in the story, however, and does form plot points in the story itself - either by being remarked upon by other characters or used to show how regional cultural differences.
Unfortunately, Dark Horse never finished publishing the series and only volumes 1 to 3 are available in English. The manga itself is out of print and very rare and can only be found used at such places as Amazon. If you can find Club 9 though, I would highly recommend it. It is an interesting work of art in the character design and use of language as well as being a hilarious and engaging story.