My original tumblr post was here. The image is a pulp magazine cover containing the text “Thrilling Wonder Stories. A Thrilling Publication. Featured Novelets: Planet of the Small Men, by Murray Leinster; There Shall Be No Darkness, by James Blish; Journey for Seven, by John D. MacDonald.” The image was first posted on tumblr by Pulp Covers and comes to us via thehauntedrocket.