For me, it really depends on how interesting the topic is- if it's interesting to me, I can read whatever it is all the way through. But, on the other hand, if the topic is boring, I can barely get through a paragraph. I also have a hard time absorbing the content of the reading if I find it boring.
I don't really have much time to read for fun, as I typically have a good amount of reading to do for courses as well as other work, and I'm also doing a lot of job hunting these days.
I'm very picky about what I choose for recreational reading; I generally like magazines of a topic of interest to me. If I find a book that I absolutely enjoy, I can sit there forever and read the whole thing. So in the rare instances where I would buy a book, I really make sure that it's something I'll like. I also do a lot of reading on the computer screen as well!