The stars were thinning out; the glare of the Milky Way was dimming into a pale ghost of the glory he had known—and, when he was ready, would know again. He was back, precisely where he wished to be, in the space that men called real.
This passage comes at the end of Bowman's transformation to a Star-Child. He is made immortal and led back to the part of the universe he had originally inhabited, to face the world from an entirely different perspective. The end of this passage emphasizes the breadth of the universe as compared to man's knowledge of it. Bowman has been brought back to "the space that men called real," not the space that is real, since as he and the reader know, Bowman has been through far more than men know of or could acknowledge exists.