Isaac Asimov has been discussed here several times already. So instead of presenting you with his biography, I'll just say that when he was at the height of his powers he was the best there was. It's too bad that he sullied his own reputation with some inferior books. Par for the course, I guess.
Published in 1950, Pebble in the Sky isn't Asimov at his best. It's an earlier work, and in it you can see that he was still polishing his craft. It's definitely better than a lot of the other science fiction of the time, but it's not nearly as good as later books/stories like Foundation and I, Robot.
In the novel Joseph Schwarz is accidentally teleported into the future, where the Galactic Empire rules countless planets, in several galaxies. Among these planets is Earth, a backwater that may have some claim to historical greatness. While Schwarz acclimates to the future, a noted Archaeologist, Bel Arvardan, visits Earth to investigate what Earth's prehistory might have to say about humanity's origins.
On the whole it's not as far flung as Foundation, and Asimov's background in chemistry is more evident in this novel. It exhibits some awkward word choices, and the "courtroom" scene at the end doesn't add suspense so much as bring the book to a screeching halt. Some of the characters are entirely too credulous, while others are blinded by prejudice to an almost supernatural degree. Throughout the novel it becomes increasingly obvious that Schwarz is a stand-in for the author, and through the Earthmen's treatment at the hands of the Galactic Empire he tries to make a point about the Jewish experience in America. I don't think he quite succeeds in this endeavor.
This is not, however, to say that Pebble in the Sky is a bad book. It's actually not bad. It only suffers by comparison with other books in the same author's bibliography. In some ways it anticipates Frank Herbert's Dune by about 15 years - a barren frontier planet newly administered by an ineffective bureaucracy, a "hero" with supernatural powers, a cross-cultural romance - and in other ways it even seems to anticipate recent news items like the coronavirus, tensions between the U.S. and China, and racial violence centered around law enforcement. I don't want to make Pebble in the Sky sound TOO predictive or visionary, but in reading it you can't help but draw these conclusions.
Is it a good book? Yes. Is it an awesome book? No. It's fairly representative of the time in which it was written, though it does look forward to the better, more complex science fiction of the following decade. If you liked Foundation you'll like Pebble in the Sky, if you didn't I wouldn't bother with this one.