Reading while exercising is always an option to keep your mind entertained while your body burns it on cardio machines. However, all that jostling about on the machines can make it difficult to focus on the printed word, and reading can be a bit distracting. eDiets would like to remind you that listening to a "book on tape" is a great workout work around for reading. Find a novel or short story by your favorite author in audio form, and listen while you workout. This is great for outdoor workouts as well. Visit iTunes and check out the audiobook selections, you should have no trouble finding something to keep your attention. They even have unabridged versions of many Harry Potter books!
When reading an engrossing novel, I often tell myself I will start cleaning the kitchen when I finish this chapter and you can apply this method of thinking, but kind of in reverse, to your workout. Commit to staying on the machine until the chapter is over. Hopefully, the plot will help you keep plodding along!