Buying this bag for the second time.  First one I used daily in all conditions across the country for years, then passed on to a friend.  If you had to have only one bag, for daily commute, laptops, libraries, shopping bags, weekend trips and overnights, this is the one to get.  It's durable, un-fussy, roomie enough for a lunch, a purse, and a 17 inch laptop an iPad, files, a paperback,  plus the usual odds & ends.  If you need more space, unzip the expansion.  If you need a more structured bag, slip a slim clipboard in the back slip pocket, If you need more flexibility, take out the ruler at the top.  It's the most versatile, functional useful bag I own.