I don't get your scale, exactly. It seems to me that that's a scale of how much you want to own the book, or maybe how much you want to credit the author, but basically a cost/benefit breakdown.
If it was more a matter of how long should you wait before reading it, borrowing it from the library could go between 1 and 2. Although now that it's out in paperback, it's better to get the paperback (new or used) than to borrow from the library, because at least you won't have to haul a hardcover around with you. (It's a fast enough read that the library's 3-week loan and huge hold list won't be issues by themselves.)
no subject
If it was more a matter of how long should you wait before reading it, borrowing it from the library could go between 1 and 2. Although now that it's out in paperback, it's better to get the paperback (new or used) than to borrow from the library, because at least you won't have to haul a hardcover around with you. (It's a fast enough read that the library's 3-week loan and huge hold list won't be issues by themselves.)