"The Rival Rigelians" is a 1967 science-fiction novel by Mack Reynolds, published as one half of an Ace Double, with the other side being "Nebula Alert" by A. Bertram Chandler. "The Rival Rigelians" is an intermediate future science-fiction novel with a "galactic empire" setting and strong sociological themes.
After the first wave of human colonization of the galaxy that left thousands of isolated colonies that lost their technology and connection with earth, teams of specialists are sent out from Sol to bring the colonies back up to a modern technological level. The star Rigel has two planets, one at a level of renaissance Italy called "Genoa" and one resembling the Aztec state called "Texcoco". After a philosophical debate above their ship, the 15 specialists divide into two groups, one wanting to bring a free market economy to Genoa, and the other planning to bring a planned economy to Texcoco. The specialists have 50 years to accomplish this task, which is not a long time by their lifespans (the book mentions that the youngest are over 100), but which will involve social upheaval on both planets. The book is only around 125 pages long, but in that time, it manages to tell the downfall of both missions, as what starts as an idealistic plan to develop a planet disintegrates into a lust for personal power by both groups. This is somewhat rectified in the twist ending in the final chapter, but in general this book tells a story about how power corrupts.
This book actually does what a good short science-fiction novel should do, especially in the Ace style. The book introduces, in the first couple of pages, a science-fiction concept, with some hand-wavey elements, and then the rest of the book describes the ramifications of that concept, with (because this is Ace), some heavy doses of action. The major problem with the book is its lack of character development, with the dozen odd characters being introduced mostly by their job and a few plot-relevant characteristics (and, the two women on the expedition are a selfless martyr and a vapid seductress, unfortunately). But the book makes it clear, in a way that the average reader of the time could understand, what its point was. Like many science-fiction works at the time, what starts like it might be a paean to the technical prowess of imperial culture turns into a critique of the same. Like many of the Ace Doubles of the time, beneath its action scenes, it strikes a cautionary note.
One additional note is how my post-reading research illuminated the book for me. In the book, Reynolds seems to be critical of both Capitalist and Communist economies and societies, and it was difficult to tell where his sympathies lay. After reading the book, I found out that he came from a Socialist background and that his father was actually a Socialist presidential candidate (although from a minor party). Reynold's background is not apparent from the book, which seems to argue not for a specific system, but that humanist values are better than any system, which will always be ripe for corruption.