This is really a combination messenger bag/laptop bag.  The outer flap has a VERY roomy, zippered compartment for easy access to smaller items, but which will easily fit a standard compact umbrella and still zip shut. It secures closed by both a velcro strip and two robust snap-close clips.

Lift up the flap and you'll find two vertical, velcro-close pouches, about the dimensions of a checkbook, but much larger and fuller.  Perfect for storing all your USB cables, connectors, small notebooks, whatever.  In between them are two slots, each of which will hold a regular pen or pencil or even a Tide pen! (I have one of both!)

On either side of the bag are two net bags, just the right size to hold a travel coffee mug (without handle) and an aluminum screw-top water bottle.

At the very bottom corner of the bag is a small velcro-closure pouch, perfect for holding a phone, Ipod, or, in my case, a multi-tool and LED flashlight!

Now for the inside.  You have one non-closeable large main compartment, which will fit an 11x17 ream of paper without batting an eye.  Plenty of room.

Immediately behind that compartment is a reasonably padded, zip-close compartment that will hold  a laptop, power brick, CAT-5 cable a router, several instruction manuals and lunch! Seriously, the interior of this bag is YUGE! You've got a lot of room here, and I like it this way.

The bag has both a carrying handle for holding it like a briefcase, and a strap for carrying over the shoulder; the strap has a nice, thick pad for cushioning the weight of the bag on your shoulder.

My only real issue with this bag is that the carrying strap is not mounted on swivels, so it's very easy for the strap to get twisted, and the pad can get flipped around.  Other than this minor inconvenience, if you're looking for a messenger bag that holds more than the average, has plenty of compartments for your stuff and is ready for foul weather, a hike in the mountains or a commute to work, this bag works!