I can't say enough good things about this bag. I just went back to school full-time and needed something to carry all of my stuff. I bought the size medium and it has more than enough room for books, notebooks, calculator, etc. The strap is very well padded considering all the weight that the bag has to carry. The pocket for the phone (on the strap) fits my phone perfectly and the extra pockets hold everything else. Recommend this messenger bag very highly.
I bought the large size, and it's HUGE. Sometimes I think it's too big (I'm 5'3"). With that said, it does hold everything (my paperwork, lunch box, 32 oz. Nalgene bottle, sweater, etc.) with no issues-- and I feel safer carrying this around downtown L.A. than my purse. There's lots of components for my little things as well (keys, I.D. badge, wallet, cellphone, glasses, etc.) I use it everyday for work, and I love it.
i bought this bag for my daughter who is a college student. She absolutely loves tis bag and takes it everywhere!!! It zipps closed under the flap so the contents are secure. I wish I had purchased one for myself to use for travel and for the upcoming christmas shopping season!!