Firstly, try to step into the world of literature you are reading. Don't just read the words on the page, visualize them. If there is a tree, don't just read about it, picture it in your mind. If the wind is blowing, imagine it's effect on the tree, how the leaves move with each movement of air.
Secondly, make your reading area unlike your sleeping area. If you sleep with the radio on, then shut it off. If you don't like lights on when you're asleep, then turn on the lights. Make the area you read in an area that feels almost uncomfortable to sleep in. This will keep you from becoming drowsy and dozing off mid-page.
Thirdly, determine what you are supposed to get from the reading material. If you're reading for a book report, then take occasional breaks to put what you are reading into some kind of context that you could apply into the report.
Fourthly, take a break once in a while. Some books are a little too stale for 'hours on end' reading and are more suited to small doses in large numbers.
Fifthly, pour a cup of coffee/tea and dig into the book if you just have to get the book read for school or for a work project. It may not be the most exciting material you've ever read, but if you can come away from it with a substantial knowledge of the material, someone will appreciate your effort, even if they don't say so to your face.
How to Avoid Getting Bored While Reading - wikiHow