I have a soapstone stove and love it.!!
Here's how it goes.
firebox is 2 layers of 1" thick soapstone....total of 2"
My stove is rated at 73% efficient and is non-catalytic
I heat 2100 sq ft of house...single story
Takes about 30 minutes of a fire in the box to start feeling any heat from the top or sides of the stove.
Puts out an even heat and after the fire goes out? It still puts out some level of warm heat for up to another 4 hours.
Once the stove "heats up" to about 400-500º F, it can and will run you out of the house. DAMHIKT!!!!!!!
A key thing to remember on these stoves is it takes longer to cool down.
At the start of every "heating" season...the stove has to be "made ready". Build a small fire in the box and warm the stove to about 100º F. Allow to cool and build a warmer fire in the box. Allow to cool and then you are ready for the winter heating. Warranty stops you at 600º F and is considered an "over fire". We run ours up to and sometimes just over 500º F about once each day in the primary heating season to keep down the build up creosote.
BTW, the "making the stove ready" is to drive humidity/moisture out of the stone from it sitting around in spring, summer, and fall. It's a porous stone and does absorb moisture when it's not in use.....Just like the wood furniture in your house.