Heaters require open air for the flow of air and to cool themselves.
Fireplace heaters go into insulated openings with flues that have safety measures in place to prevent the heat of the fire from igniting the walls of the chimney and where the fires are.
So no, you can't bring home what is basically a space heater, plug it in, and sit it in a bookshelf. You have to be able to feel the wall around and above the plus so you can see if the wall is getting hot. If it is? Then you could have a fire start inside the wall. If the plug is hot you can have a fire that is electrical that would short out the entire unit electricity and have a massive fire breaking out from every plug in or appliance.
If you don't have propane heat or natural gas heat or live in a total electric home then you really need to figure out what you're trying to do.
I live in a mobile home that has a minimal roof and a plastic bladder that covers the stuff underneath the floor. My heat goes out the window glass, through the roof, and through any cracks in the floors around heater vents, carpet tacks, etc...
I put a small ceramic heater in my sitting area. I plug it in directly to a wall socket. It is NOT safe to use any sort of extension cord or anything that isn't direct. I turn it on when I'm sitting here watching TV or on the computer. I feel the wall to make sure it's not overheating. I sit on a blanket so the backs of my legs are not exposed to the room air. I wrap this blanket around my feet and legs. I open it up and sit closer to the ceramic heater when I'm very cold. I do not leave it on when I'm not in the room or when I leave.
I have huge comforter's over the windows in every room. These block the cold air coming in and the warm air going out. I make sure they stay covering the windows.
I am responsible for finding ways to keep myself warm.