The speaker is resting, and the place they rest in is strange: "green and red books" that turn out to be "a great library of rust." Oxidation is slow decay, so the title and images suggest something, or someone, quietly wearing down. The books may be actual old volumes, or they may be a way of picturing a life made of stored-up pages that are now flaking away.
What the speaker feels seems to be a calm, almost flat stillness. They have "nothing to do / and nothing not to do," which sounds like freedom but also like having no purpose pulling in any direction. Nothing is demanded, and nothing is forbidden.
Then the last line drops in "one match." It's small, and it changes the mood. A match can mean destruction, since a library of rust and paper is a sad thing to set alight, but it can also mean possibility or release. The poem leaves that choice open, so the quiet ends with a faint, unsettling tension.