The wood is about half the thickness of tongue and groove and made up to 9 panels (a couple of dowels and wood overlays to bind them together, a pre-built 'drop-in' floor and a felt roof with screws that will need to go through the felt. Two shelves are sturdy enough. The instructions are picture-based with an Ikea-feel but without the allen key. You will need an electric screwdriver.
The pre-drilled holes, little think plywood guide squares, numbered pieces make it easy. It's nice looking. My son came to inspect, opened the doors and the whole think shakes a bit "It's a bit flimsy isn't it?" he said. I can always add a few metal brackets to give it a bit more strength, but its not really built for security. The bolts are almost cosmetic than functional and no padlock, but then with only 2cm No4 tiny hinge screws, I don't think a padlock will make a lot of difference anyway.
This is not as strong as the normal T&G on your garden shed, but I'd say its enough for Garden tools. I wouldn't store anything expensive in an exposed area, since even with security screws and bigger bolts, the panels look like they would give in easily.