The Book: Secret of the Black Planet by Milton Lesser. According to the ISFDB, originally published as two shorter stories in June and July of 1951. The edition read was printed by Belmont in 1965.

The Setting: Earth, Space and Really really distant planets, all in a not that distant future.
The Story: A strong man in a circus is really a famous space archaeologist who has discovered a secret of eternal life and now people are trying to kill him. Then, the strong man/archaeologist’s son and a girl travel the universe trying to find who first found the secret of eternal life, and love. Also Martians, Venusians, and competing planetary mobs.
The Science: Uh. Okay. So. You sit in this chair in this mysterious “black planet” hanging out in the asteroid belt, do some stuff, and you get infused with life, strength, the ability to heal, and, what the hell, you can even come back after being killed-but-good. BUT! If you sit in that chair too long, you’ll age in reverse until you’re not even a twinkle in your daddy’s eye. In that second scenario, something is seriously wrong with the law of conservation of mass, because no energy seems to be given off in the reaction.
Don’t even getting me started on the teleportation issues.
The Reaction: I liked that it was an adventure story for a while. It was very much in the spirit of John Carter, and that was fun. When it’s fun, I don’t care that it’s not making much sense. But this book committed a cardinal sin, in the area of formatting. In many places, SECTION BREAKS ARE OMITTED. You might not think section breaks are important, but when you’re jumping between two scenes, and there’s no space between the paragraphs to alert you, it gets confusing. Confusing pulls you out of the story. It all ends in rage. Bad editor, bad bad editor.
The Cover: Formatting issues aside, this cover is awesome. Alas, no credit for the illustrator. There’s a spaceship, there’s a dude with a ray gun in his long johns, and there’s a girl straight out of the ’40’s hanging back. Also, that font. I love a font. The only problem is that the blurbs on the front and back cover seem to have been written by someone who read a different story.
Next Up: “Feedback” by Katherine MacLean