For books I HAVE to finish one before moving on to the next one, or else I will never finish it. This is actually a problem for me... I'll start reading one, get bored half way through or find something else I'd rather read, move on and never feel like picking up the previous book again. I pretty much have to tell myself, "Ok, finish this book. You cannot pick up anything else until this one is done." And sometimes I'll end up with a stack of books waiting to be read.
Its actually pretty rare that I start reading a book and just cant put it down. Those real page turners are rare but I get one every now and then, for everything else...reeding iz haaardd.
On the bright side, as sad is this may seem, I get a sense of accomplishment every time I finish a book.