Is the Ellison Double a hardwired fixture?

It is a wall sconce meant to be mounted on the wall as a fixed fitting. Plan for a junction box and a wall switch where you install it.

Does it point light up, down, or both?

Both. Opal glass shades sit above and below the metal knuckle, so it throws a soft glow upward and downward.

Will the opal glass be bright enough to read by?

Opal glass diffuses light, so expect a soft ambient glow rather than a focused beam. It works best as accent or mood lighting beside a mirror or in a hallway.

Dimming depends on the bulbs and the wall dimmer you use, not on the fixture itself. Use dimmable bulbs and a compatible dimmer if you want lower light.

How does it compare with a single-shade sconce?

The double adds a second shade and more visual weight, which suits wider walls and paired placements. A single sconce is slimmer and better for tight spots.