Definitely a Cabas Mezzo. I have it and I use it for work alot. You will be suprised at how much you can fit in this bag. Books, jackets, bag lunch, etc. I tend to take it to the mall with me when I know I will be doing some serious shopping.
ETA: I even used it as a carry on piece onto a plane. I fit several magazines my Chanel Cambon Bowler a huge zip lock of candy (filled with 2 king size snickers etc.) and a bunch of other random junk with room to spare. As for it holding up - it did just fine and still looks fantastic. It's a bag and is meant to be used.