Haldane, who was a committed member of the Communist Party, wrote a sort-of book review of Lewis's space trilogy in the Modern Quarterly, a Marxist journal which a few years later in fact changed its name to the Marxist Quarterly. Given the publication outlet, Haldane's review was less focused on subtle analysis of character and plot, and more focused on whether Lewis was showing too much deference to the forces of markets and money and not enough deference to the virtues of scientific planning of society by Communists.
Lewis wrote but never published in his lifetime an incomplete essay called "A Reply to Professor Haldane," which to my knowledge first appeared in 1966 in Of Other Worlds: Essays and Stories, a collection of C.S. Lewis works edited by Walter Hooper. Here, I'll quote from two paragraphs of that essay. Given that economists often find themselves defending the notion that markets should play an important role in social decision-making, and that monetary incentives are not the only mechanisms through which personal greed can operate, the passage (at least to me) offers plenty of food for thought:
The difference between us is that the Professor sees the `World' purely in terms of those threats and those allurements which depend on money. I do not. The most `worldly' society I have ever lived in is that of schoolboys: most worldly in the cruelty and arrogance of the strong, the toadyism and mutual treachery of the weak, and the unqualified snobbery of both. Nothing was so base that most members of the school proletariat would not do it, or suffer it, to win the favour of he school aristocracy: hardly any injustice too bad for the aristocracy to practice. But the class system did not in the least depend on the amount of anyone's pocket money. Who needs to care about money if most of the things he wants can be offered by cringing servility and the remainder can be taken by force? This lesson has remained with me all my life. That is one of the reasons I cannot share Professor Haldane's exaltation at the banishment of Mammon from a sixth of our planet's surface'. [Haldane was trumpeting his support for the Soviet Union.] I have already lived in a world from which Mammon was banished: it was the most wicked and miserable I have yet known. If Mammon were the only devil, it would be another matter. But where Mammon vacates the throne, how if Moloch takes his place? As Aristotle said: `Men do not become tyrants in order to keep warm.' All men, of course, desire pleasure and safety. But all men also desire power and all men desire the mere sense of being `in the know' or `in the inner ring', of now being `outsiders': a passion insufficiently studied and the chief theme of my story. When the state of society is such that money is the passport to these prizes, then of course money will be the prime temptation. But when the passport changes, the desires will remain. And there are many other possible passports: position in an official hierarchy, for instance. Even now, the ambitious and worldly man would not inevitably choose the post with the higher salary. The pleasure of being `high up and far within' may be worth the sacrifice of some income. ...
[W]as I attacking scientific planning? ...[i]f you must reduce the romance to a proposition, the proposition would be ... `Under modern conditions any effective invitation to Hell will certainly appear in the guise of scientific planning' ...Every tyrant must begin by claiming to have what his victims respect and to give what they want. The majority in most modern countries respect science and want to be planned. And, therefore, almost by definition, if any man or group wishes to enslave us it will of course describe itself as `scientific planned democracy.' It may be true that any real salvation mus equally, though by hypothesis truthfully, describe it self as `scientific planned democracy.' All the more reason to look very carefully at anything which bears that label.