I use the Yukon by Head Porter. I've used it for about two years now and I love that it's on the smaller size but still easily holds a laptop, books, notebooks with no issues. It's very minimal and comfortable to carry and I love that it doesn't use a fold closure or look too much like a hiking backpack. Also the bag is very water resistant which comes in hand a lot as I live Seattle.

http://store.headporter.co.jp/en/products/detail.php?product_id=2530