It is autumn, that time of year when thoughts turn to these gorgeous European high efficiency wood stoves that we can't get in North America because the market likes cutesy old fashioned ones like grandma used to have. The Attika Geo has the slender modern look like the rest of their line, but is made of soapstone, to hold the heat. In fact, it can pump out 7 kilowatts (23,885 BTU/hr) of heat burning 2.5 kilograms (5.5 pounds) of wood per hour, which they claim is enough to heat 215 square meters (2314 SF).
Given the slow rate at which it cools down because of the thermal mass of the soapstone, this will keep you warm all night on a couple of pieces of wood. It is also 83% efficient.
If you don't want to look at so much soapstone but do want a bit of thermal storage, they actually sell soapstone inserts as options for their other fireplaces.
I do wish there were North American manufacturers who made such sensible and beautiful fireplaces. More at Attika