I've always found this amusing because I've long known of a useful book-shopping strategy for myself: I will usually like any book that features a book on the cover. This knowledge has often proven useful when I'm at the bookstore and just scanning the shelves.
This was how I originally found John Crowley's Little, Big (it had a lovely cover featuring Smokey Barnable and Daily Alice sitting at an outdoor table, surrounded by piles of books), Charles De Lint's The Little Country (which had one large book -- surrounded by Irish countryside -- on the cover), Martha Cooley's The Archivist (which featured a stack of antique books on the cover), etc.
Generally, I figure if the book is about books, people who like books, people who work with books, or events surrounding books, I'll probably like it: Umberto Eco's The Name of the Rose, Jose Saramago's The History of the Siege of Lisbon, A.S. Byatt's Possession, Italo Calvino's If On A Winter's Night A Traveler, William Goldman's The Princess Bride, etc.
Yeah. I'm such a book nerd that I even love books about books.