Right before the offer is made, the wife of the couple is wandering home and passes a bookshop:
[S]he halted at a bookseller's window. Richard's new book on English lyric poetry was well displayed. It was selling, too, which had been a pleasant surprise. (The bookseller had explained that away rather harshly: people were buying strange books now, it sort of soothed their minds.) She smiled to herself in the window at her totally unpoetic thoughts. A selling book would be a help towards another summer among the mountains.Oh, for the days when a book on English lyric poetry might make a noticeable contribution towards an Alpine holiday!
And is it possible not to love the bookseller's befuddled honesty? As someone who spends far more of his time than he ought thinking about why people buy the books they buy, I can tell you it's not a science. "People are buying strange books now"? Right. Seems as good an answer as any.