A man inherited a field in which was an accumulation of old stone, part of an older hall. Of the old stone some had already been used in building the house in which he actually lived, not far from the old house of his fathers. Of the rest he took some and built a tower. But his friends coming perceived at once (without troubling to climb the steps) that these stones had formerly belonged to a more ancient building. So they pushed the tower over, with no little labour, and in order to look for hidden carvings and inscriptions, or to discover whence the man's distant forefathers had obtained their building material. Some suspecting a deposit of coal under the soil began to dig for it, and forgot even the stones. They all said: 'This tower is most interesting.' But they also said (after pushing it over): 'What a muddle it is in!' And even the man's own descendants, who might have been expected to consider what he had been about, were heard to murmur: 'He is such an odd fellow! Imagine using these old stones just to build a nonsensical tower! Why did not he restore the old house? he had no sense of proportion.' But from the top of that tower the man had been able to look out upon the sea.This is a collection of seven lectures by Tolkien, of which I think I had previously read only "On Fairy Stories" and "A Secret Vice". As always, they are an interesting insight into how his mind worked, or at least how he wanted us to think it worked. The more academic pieces (in particular the second, "On Translating Beowulf") are somewhat moored in academic controversies of their time, which may or may not have subsided by now and which in any case I am not close to. But the title piece rises above that to give an argument for appreciating Beowulf as a real story with serious monsters, rather than just a source for scholarly discussion on vaguely related topics, and that is the point made in the vivid metaphor of the man who built his tower on inherited land.
The other highlight for me, even as a non-Welsh speaker, is the lecture "English and Welsh" urging those with an interest in the history of the English language not to ignore its nearest geographical neighbour. He makes the same general point made much later by McWhorter, that English shares a significant substratum with Welsh (and he is very insistent that it is Welsh/British rather than the Goidelic languages), though interestingly uses a completely different set of linguistic/grammatical clues to McWhorter in making the argument. So there may well be something to it.
"On Fairy Stories" has quite a lot of information about Tolkien's views of other works of fantasy literature, ancient and modern; it is a bit less successful at setting up an analytical framework for looking at fairy stories as a whole (Farah Mendlesohn seems to me to have a more useful and more widely applicable approach), but again he makes a convincing emotional appeal to treat the stories first and foremost as stories for an intended audience, rather than for anything else. His valedictory address, at the end of the book, is an amusing but somewhat rambling justification for wandering off the point for most of his career, but in fact a commitment to an aesthetic of narrative seems to have been precisely the point, one which he successfully communicated through both his fiction and his non-fiction.