Mark Strand is known for his simple diction, surrealist imagery, and narrative techniques. In other words, he writes straightforward poems that tell a little story and often use surrealism.
"Keeping Things Whole" is no exception. The language is clear and precise and the imagery is surreal in the sense that we're trying to see a speaker who embodies "what is missing." We could also say the image of a body parting air as it walks is surreal.
Strand's other obsession is the double-ness of human beings. His poems often deal with consciousness and paranoia, a sense that the speaker feels alienated from himself and coexists in two different frames of mind. So if you come across a free verse poem that sounds simple, has some really strange images, and refers to a speaker who is lonely, alienated, or has a fragmented sense of self, well, you just might be reading a Mark Strand poem. And it just might blow your mind.