Not one "hook", but four, here: Jane Austen (literature); a travel narrative; a romantic angle; being "Christian" -- all contained in the full title. Here's how each worked for me ...
I read Austen's books (unabridged audio), except Sanditon years ago, and remember virtually nothing about any of them. Others may have found her treatment of Jane's life "superficial"; I didn't really care all that much, seeing it as basically something around which to frame her itinerary.
The travel angle worked well for me. Smith was actually pretty funny in describing her predicaments and challenges. I admired her for using public transport as much as possible so successfully.
Her thoughts on "love" spun off from a crush on (an American) guy she met the first week in Oxford, who mentions wanting to get together after they return from their separate journeys. Not being an older, single, evangelical female, I tuned out her complaints regarding the difficulty of finding a mate. Fortunately, this aspect surfaces primarily at the beginning and end of the book.
Finally, and most frustratingly, there's the "Christian" business - Smith seems to be almost disingenuously trying to "have it both ways"; she's from (what I would consider) a fundamentalist background, but mentions her disillusionment with strict fundamentalism, referring to herself as an evangelical; she was never a teetotaller (nor is her family), making regular reference to her wine consumption since a teenager. I just couldn't shake the feeling that she was trying to hook "Christian" readers, while at the same time trying to ummmm ... "reassure" secular ones that she had evolved past fundamentalism.
Bottom line: it depends which "parts" work for each person, as they don't come together (enough) for a whole.
I was very surprised by how much I enjoyed this book! I found it to be a memoir filled with insights and occasionally, wisdom. It is a very personal book that resonated with me.
Love Smith's writing style -- I felt like we were just sitting together having tea while she was telling me her story. And since I love England and all things Jane Austen, I was riveted by her story!