The front cover has light wear - about VG+; spine has 1/8" tilt, some edgewear next to back and wear to lower half, along with some raise wrinkles (as printed) which make it look like it has more wear - about VG; back cover has fold traces on left corners, general wear and heavy rubbing wear - Good+ No writing or marks - a clean copy.

The Black Flame, by Stanley G. Weinbaum. Stanley Weinbaum is somewhat of an early legend in early SF for producting a couple dozen quality SF stories in his tragically short career in the mid-Thirties. He also had a couple of novels, published posthumously - this is the combination of both "Margaret of Urbs" novels: "Dawn of Flame" + "The Black Flame." Both stories were published posthumously, after Weinbaum's popularity was well-established. The back cover doesn't have much in the way of plot summary, but here it is: "CIVILIZATION HAD DIED SCREAMING in a blaze of nuclear and biologican warfare. Gradually, during the Dark Centuries that followed, secrets were re-discovered, and new knowledge gained. Finally, the key to immortality is found, and the preternaturally beautiful Margaret Smith becomes Margot of Urbs and, with her brother, begins a relentless drive to absolute power..."

I know of one other paperback - from Harlequin in 1953 (good luck finding one...) This may not be fabulously rare, but I think it quite uncommon. In 35 years of collecting SF and haunting used bookstores, I haven't seen many copies in good shape.