Up to about 20L/35L capacity, it's not a big backpack, better to be a daypack.
The main compartment with two little compartments inside - the bigger fits an I-pad, the smaller one is zippered to hold all the small things you carry with you. The main compartment has zippers all the way, so getting something out of even a fully packed rucksack is fast and easy.
Shoulder straps are well padded and contoured. The waist strap can be easily removed if you don't need.
Good compression straps, two on each side and two on the underside - this thing can be compressed to the size of a hydration pack. Size compression straps have quick releases, which is a very handy thing. The straps also double as an easy way to strap stuff on to the pack - strapping your jacket onto the pack when moving indoors has never been easier.
Hydration pack pouch on the inside (hydration bladder not included). If your bladder is too long, just fold it.