If I don't see finishing the book as rewarding then I stop.

If you want to know whether you should, I would suggest you try to finish it out. There's a reason you picked it up in the first place and you never know how it will turn out.

If you want my experience, basically what
>>8232812
said.

To be more specific on how I determine if I think it will be "rewarding":

It depends. How "important" it is in terms of "canon" or influence on later works/writers? How much do I dislike it and why? How many other things am I reading at the time (if there's a couple others, I'll end up spending more time on those and just won't get back to it). Why did I choose to read that (is it part of a certain era or movement or on a particular topic I'm reading a lot of at the time? A work by an author who I've read and enjoyed other works? Was it recommended by someone?)? Etc.

In general, I try to finish everything I start but sometimes I just don't, especially if it's not related to other things I'm reading.

Most recently I was really forcing myself to get through Johnny Got His Gun, but kept going only because it was recommended by someone who I had developed a pretty close relationship with and it seemed important to her. As it turned out, the book went fron something I was hating for the first 95 pages or so to a work that is easily among my favorites of what I've read in at least the last several months.

>>8232778
For some reason, I just could not get through the beginning of atlas shrugged.

I would stop after the first couple pages and leave the book for a time, only to have to start over.

Finally I said fuck it and just read, and read, and it turned out to be one of the best I have ever read

Any thought-out plot is going to fluctuate in momentum. It's even possible that an author may spend 400 pages all to build up a single moment. I try not to fall into the snare of instant gratification and carry on.

i know within a few pages whether im gonna finish it or not, if the prose is good enough i'll finish anything.

>>8232778
I always try to push through because sometimes it gets good, I normally end up setting it down and just not ever coming back to it if I really don't like it.
So far there's only been two books that I can think of that I just had to stop reading, and those were "The Key to Midnight" by Dean Koontz, and "Red Storm Rising" by Tom Clancy, but I might give the Clancy one a second try.

>>8232812
How do you know whether or not finishing the book will be rewarding if you don't finish it?

Yes but I would have quit the book at least 5 times until I put it down for good.

Stoner was one such book. Heavily appraised and lauded here, I couldn't finish it due to extreme boredom and the dry prose style. I did give it a chance, I read the first 3/4 of the novel in the span of 6 months. I may finish it soon but there are better works I'm reading in the meanwhile.

>>8233103
If it's educational, interesting, entertaining then I won't put it down. If it is none of those things then I have to make a decision whether to drop the book and give up on the idea of it being worthwhile any longer. If I'm 3/4 of the way through a book and it doesn't seem worth reading then Im content in my decision that the last quarter will continue the trend.