That's when I make a decision, as a reader.
I've been reading since I was little. Granted, I wasn't reading books with more than 50 pages, or anything containing sex scenes, but I'm sure I had a system even then to distinguish between what I wanted, and what I didn't want. It probably related to illustrations and inclusion of, or lack of, kitty cats.
Now that I'm older I've got a handy little thing called Goodreads that I use to make my list of "to-reads." And oh my, friends, that last is long. So long that I really should consider breaking a leg or devising a bed rest of some sort here soon.
I exercise, I eat (somewhat) healthy, I've got a pretty clear family history when it comes to the really bad health words. But... I've got a nagging sensation that I won't ever be able to read all the books that I want to read before you know - I 'm dead.
That's because I work in a library, and every box I open tends to add another 4-5 books to the "to-read" list, whereas every week I chalk up at the most 2 on the "read" list. It's not a good ratio. So I'm re-instituting a rule I devised in college, when pleasure reading took a backseat (pun intended) to the meatier (pun intended) stuff.
50 Pages or A Sex Scene
That's right. If I could give less of a crap about the characters or plot in the first 50 pages OR if I get to sex scene that does absolutely nothing for me, then the book is dead to me, and it goes on the "not-to-be-read" pile.
Granted, some books have a sex scene much quicker than others. The most memorable early sex scene I can remember was a Page Two event that really did nothing for me, but I kept going because I was intrigued by the balls it took to just throw that out there. In the end, the book was crap, but it was a lesson learned.
What's your rule? When do you decide to part ways with the not-so-awesome plot?