How fast does it heat up?

Ceramic heaters reach working temperature in seconds, so warm air starts within moments of switching on. It is faster than an oil-filled radiator, which needs minutes.

Is it loud enough to disturb sleep?

The fan is audible, and owners most often mention noise at the higher setting. On a low setting it is quieter, but light sleepers may still notice it.

Can it heat a whole living room?

It is a spot heater. It warms the area in front of it well but will not bring a large open room up to temperature the way a full-size convection heater would.

Does it need assembly or installation?

No. It is a plug-in appliance that works out of the box, with no mounting or wiring.

Is it safe to leave running unattended?

Follow the manufacturer's instructions. The housing gets hot in use, so keep it clear of curtains, bedding and anything flammable, and do not cover it.