Cult Swedish label COS arrived stateside this month with a pop-up shop at New York's Opening Ceremony to try out the US market. (A New York retail location opens next year.) The brand, owned by H&M, creates upscale, no-nonsense wardrobe building blocks--think sleek, moderately priced wool coats and unadorned cotton tops. Eager American minimalists got so excited when COS pieces became available at Opening Ceremony, they crashed the company's website.With a hyped-up collection this utilitarian, it’s almost a relief to find one piece that eschews practicality: a leather button-down shirt. Prim without being prissy, this top is easily the most expensive item in the collection at $400, but might just represent the coveted middle ground between librarian and Hell's Angel.