We have all been told one time or another not to judge a book by its cover. Naturally, this advice makes good sense, unless you are looking at a cover simply to quickly gauge whether it is a genre you like to read or are willing to experiment with. If I judged by the cover, I would not have picked up The Berlin Boxing Club, for example. And that would have been my loss.
But aside from the cover, when do you decide whether a certain novel is one you want to read or leave on the shelf?
Is it the blurb on the inside jacket?
The first page?
The first paragraph?
Or just the first sentence?
I usually buy my books in a physical bookstore - there is something about being in the presence of so many works that simply cannot be had by clicking "add to basket" or "checkout." I will select books randomly, regardless of cover. I skip the blurb and go straight to the first page.
If I am hooked, I am hooked after the first sentence. ("The year was 1937; the month was September, the evening unseasonably cold.") If I am not fully satisfied, I will read the rest of the paragraph and, most often, the rest of the page. If the story and I do not connect after that first page, chances are we won't and the book is going back onto the shelf. Style and theme, in my opinion, do come across almost right away.
How do you judge a book?