Tarzan, his monkey friend Nkima, and Chief Muviro and his faithful Waziri warriors prevent Soviet communists from looting the lost city of Opar. The story also prominently features Tarzan's lion ally Jad-bal-ja.

Goodreads Member: Frank liked it & rated it 3 of 5 stars: ''When I was 10 years old, my father gave me three books for Christmas: Treasure Island, The Swiss Family Robinson, and Tarzan and the Golden Lion. At the time, these were all a little advanced for me but when I reached my teen years, I finally read the Tarzan book and was hooked on his adventures. My older brother also had a copy of Tarzan and the Ant Men which I still consider one of the best in the series.''

''In the 80s, I decided to read all of the Tarzan adventures in order but only made it as far as Tarzan at the Earth's Core and then for some reason I stopped reading them. In the mean time, I started collecting Burroughs editions in hard cover and now have a near-complete set of his books. So I kept seeing the books on their shelves and decided to read the next Tarzan adventure, Tarzan the Invincible.''

Goodreads Member: Qt really liked it & rated it 4 of 5 stars: I thought this was a fun one! Some of the later Tarzan books that I've read recently hadn't really held my interest, but this one, like many of the earlier books in the series, was fun, fast-paced, and full of adventure.