I expect nothing less from Konno Kita, who writes some of the most peaceful and lovely short stories I've ever had the pleasure of reading. If you're the type who expects melodramatic romance and a run-of-the-mill love triangle the moment you see that the demographic is josei, I don't recommend Cotton at all. There are subtle themes of romance (not GL) in most of the stories, but it's done in a way that's very calm and mature (in the adult, prudent sense; not in the smut sense). This might sound boring and uneventful to the average romance novel/manga fan, but being free of the typical love drama makes it very refreshing to me personally.
Also, I'd like correct the false impressions that tekiteki's comment will undoubtedly engender. While I'm sorry that she fell in love with someone who played with her feelings, that is patently irrelevant to Cotton, and I'm befuddled as to why she found it necessary to spill out her sob-story here. Michiko is a kid who is simultaneously spoilt and lonely, and who, because of her upbringing, is incapable of connecting with people in and around her own age. She's the one who latches on to Natsuki, not the other way around, and she's nowhere near clever or cunning enough to toy with the older woman's emotions. She "made Natsuki cry" because she thought the only person she'd ever befriended was indulging her with ulterior motives in mind, and she "told her she loved her" when she realised this was not the case. Natsuki is not in love with Michiko: she has a good relationship with a nice guy and I highly doubt that she'll jeopardise it to chase after Michiko like tekiteki seems to think she will. I'm not saying Michiko's a great girl, because she isn't, but she makes a much more interesting character for the story to explore than a "great girl" ever could have, and there are definite hints towards the end that her entitled attitude is improving - if only bit by bit - due to Natsuki's guidance.
The other oneshots, while too short to warrant individual comments, leave you with the same feeling of sedate happiness, though the themes and mood of each one are different to those of the title story.
All in all, a charming little collection that's great for a quick read, especially when you're feeling stressed.