The 1973 edition is still in print and still selling . Why? Because the physics hasn't changed. General relativity is a classical field theory. The mathematics of curved spacetime was frozen in 1915. A book written in 1973 about a theory from 1915 is just as accurate today as it was then—unless you care about dark energy (which isn't covered) or loop quantum gravity (which doesn't exist).
The "Big Black Book": A Legacy of Misner, Thorne, and Wheeler’s Gravitation The 1973 edition is still in print and still selling
MTW is famous for its unique visual style. It is packed with hand-drawn diagrams, "boxes" containing side-bar derivations, and "vignettes" that explain the history of the field. The prose is often poetic, reflecting Wheeler’s belief that "spacetime tells matter how to move; matter tells spacetime how to curve." General relativity is a classical field theory