On a treadmill, you walk. Walking isn't that fun. You can walk at different speeds, but that isn't really much more fun. If you get a treadmill that offers an incline, that keeps it a bit more interesting. Walking uphill isn't exactly fun, but it's different. It presents a challenge. You can't really read on a treadmill because you are bouncing up and down. You can't keep your eyes on the same sentence, and you usually end up with a headache. Basically, the only thing fun to do on a treadmill is watch television or movies. If you are really into TV or movies and are able to put your treadmill in front of a television, you can probably keep your treadmill workout from becoming too boring.