Quite a good purchase for my 13" MacBook Air.
The first impression you get is that it is a bag of quite good quality construction.
The laptop is protected on the sides by a specially shaped body, while there is space for carrying documents and some folders, possibly.
The charger fits comfortably in the side pockets, which slightly protrudes (without being squeezed), the magic mouse, as well as some charger cables.
Satechi is a brand known for its quality implementations. The future will show its durability over time.

I bought it and it seems quite high-quality and waterproof construction. It has good protection for the laptop on its large surfaces (top and bottom), moderate protection in terms of thickness. It is only handheld, not shoulder. It does not provide a strap nor does it have provision to attach a shoulder strap. The space for a computer of this size is satisfactory, at least for me.
Update: After a year of use, the bag is like new. Completely satisfied.