On the latest Pop Culture Happy Hour they had this topic, to which I'll offer some response: When is it okay to give up on a book (and then they extrapolated out to discontinuing watching a TV series, walking out of a movie, leaving a theatrical performance)?
The answer is ridiculously simple: if you are not specifically required to read (or watch) something (for school, for work, for a book club, to keep up with what people are tweeting about, etc.), then it's a simple determination: when you're not enjoying it, getting nothing out of it.
But the trouble is that we're led to believe quitting is bad, so we force ourselves to finish a book (or show) out of obligation, even when it has passed the point where we are doing so of what could be considered our own volition. Also, there's a sense that if we abandon the book before reaching the end we may miss out on something that ultimately was worthwhile (but started poorly) and we'll regret it; the pushing forward is a means of avoiding that regret (and there is some benefit there).
If something is so actively bad that you can get some enjoyment out of marveling at its ineptitude and being able to mock it, that can be more than adequate to justify keeping at it, but if something is not so bad as to provide that, then it's worth bearing in mind that life is short and unless you have just a surfeit of time or feel compelled to punish yourself (or simply need something new to complain about on the internet), give up on that unsatisfying book (or TV series).
Movies and plays/musicals (live theatre) tend to only be a couple hours and are awkward to walk out of during the show, so those really have to be awfully non-rewarding (even for mockery) to quit, but TV series go on for show after show, all season (and sometimes season after season), so those do turn into a serious time commitment to keep watching. But now that there's the relative ubiquity of DVR technology, and their capacities keep getting larger, the option to record a number of episodes with a vague optimism that it might be worth watching if one later feels like diving into watching but without having to actually watch as the episodes air. It's wonderfully non-committal while still holding the opportunity to commit. And then after one still hasn't felt compelled to start watching after months have passed and one needs to clear out some free space on the DVR one can delete the show.
I imagine the Kindle or iPad offer a similar opportunity to get something and have it merely taking up some hard drive space, but not having such a device I can only assume. But it still boils down to it being easier to amass content that one may eventually choose to read/watch at a later time, conceivably when one finds oneself with a surplus of free time (perhaps if one is bedridden, or on house arrest, or those lottery numbers come up, etc.) without books stacking up on shelves or video tapes piled by the VCR. If technology exists for any purpose is it not ultimately to cater to our gluttonous appetites for media (that defies logic but which we still fancy we can somehow consume)?
It's a good time to be alive.