To me the most amusing (and sort of ironic) side of Tolkien's criticism of Narnia is his reported reaction — something like "It won't do, you know!" — when Lewis introduced Father Christmas into the first story. This from the man who spent YEARS, every single Christmas time, writing and illustrating the most beautiful letters to his own four children "from" Father Christmas and all his friends at the North Pole...!!! Apparently it was perfectly OK with him for Father Christmas to exist in our world, to have all sorts of adventures and to keep up an annual correspondence with the young Tolkiens, but not for him to be in someone else's fantasy story about children from our world entering into a different one (and if they can travel between worlds, after all, why can't Father C?)... Seriously, though, I don't think I've yet seen any scholarly commentaries on Lewis and Tolkien that address that aspect of it.

As for the rest of Tolkien's criticisms, I don't know if I know enough to comment. I think the recent book about Tolkien's "modern reading" — or was it another recent publication about JRRT? — goes into Tolkien's response to Narnia and suggests that Tolkien in fact wasn't nearly as critical of Lewis's world-building as most people have assumed. That's just something I picked up from a review I read, however — I haven't read the actual book — so if anyone else here has, I'd be very interested to know what that author concludes.

@courtenay

This article from 2013 may not be from the book you are referring to, but I looked up “Tolkien’s Disparaging Narnia “ on the Google search and it came up along with a couple of other articles:

https://dc.swosu.edu/cgi/viewcontent.cgi?article=1095&context=mythlore

I hope it might be of some help.

@narnian78 That article looks really really interesting, thank you! I don't have time to read it all now (it's late here in the UK), but I will in the next day or two.

The book I was thinking of is Tolkien's Modern Reading by Dr Holly Ordway, published earlier this year. Johobbit posted about it some months ago in the Tolkien thread and gave a link to this article by the author, which I can see is where I picked up the assertion that Tolkien "didn't detest C.S. Lewis's Narnia Chronicles".

Unfortunately the article doesn't go into any details of how Dr Ordway came to that conclusion, so I guess one has to read her book to find out!! Have you read any of it yet, @jo, if you don't mind me asking? I'd love to hear more about it, especially whatever she has to say about Tolkien's view of Narnia.

*pops in* to say that no, I have not begun Ordway's book, as I have so many books on my to-read list before this one. And given the type of book it is (more academic reading), I will probably take a chapter at a time, with breaks, rather than read the entirety in 'one fell swoop'.