Title: Does it sound good? Go to Amazon and look at the most popular books of the recent year. The top five I'm seeing are: The Tea Planter's Wife, After You, A Brief History of Seven Killings, The Girl on the Train, and The Aeronauts' Windlass. Can you tell which is the best title? It's easy to guess, but why that is is a matter of experience: titles that contain "X's Wife" or "The Girl ..." are uninspired and seem to be designed to a trend, generally a true reflection on their books; After You is similarly reminiscent of bad books; and The Aeronaut's Windlass is a meaningless combination with the sound of brainless jargon-filled pulp. A Brief History of Seven Killings skews dangerously close to the drastic quaintness of recent popular literary authors (Brief Wondrous Life of Oscar Wao, Extremely Loud and Incredibly Close, A Highly Unlikely Scenario), and it's similar to A History of Violence (not an impressive association), but the thing is, it's evocative. It sounds expansive, brazen and modern - not extraordinarily so, maybe, but there it is - and that's accurate to the book. Keep going: The Shepherd's Crown, Ocean of Storms, Go Set a Watchman, Strange Child, Varieties of Exile, American Gods, Walk Into Silence, Rebecca, Catch-22, Blood Lines, Rather Be the Devil, Dark Water, From Sand and Ash, His Only Son, The Post-Office Girl.
Cover: Does it look good? That is, does it please you, and/or, does it stay clear of tackiness? I'm not of the opinion that a cover based on a screen adaptation is damning at all, they just look bad, and besides, they are often put on classics (in the case of a translation, though, it may indicate a less than serious attempt to present a definitive edition). But I believe that good illustration tend to appear on good books, certainly preferable covers (for example, the Paul Hogarth illustration for Animal Farm vs the Signet Classic cover, or the original Great Gatsby cover vs DiCaprio). For two reasons: One, it is nearly a rule that there's an inverse relationship between quality and market value in the arts, just as there is a parallel between market value and marketer interference, and while a major publisher in the push towards mainstream revenues will tailor the book to resemble previous successes, smaller publishers (not always, and not all, but a beautiful few occasionally) will tailor the book to best represent its contents, which by their quality will appeal to discerning readers (or by their fashionability to superficial ones). The second reason is, good illustrators have good taste, even in literature, sometimes, and if given an inspiring commission, which is more likely from a press that takes risks on ambitious and genuine work, they rise to the task.
First line: Like it? Want to keep reading? Sometimes the first line of a good book is modest. If they don't take a big swing in the first line, they do in the last, and if they don't you can't tell.