Unless you're only taking one or two classes, I'd stick with two straps. They distribute the weight much better. I've had good luck w/ a laptop bag from Wenger/SwissGear. Got it at Bestbuy but they may have discontinued the exact model. I max the volume out @ 40lbs of book, notebooks, & laptop (can't fit anymore in). The only change I'd make to the one I've got would be to add a hip belt but that would only be in the way depending on how heavy the book load is MWF vs TR.