I have had an interest in masonry stoves, aka Russian
heaters, they are primarly designed for heating, however, I have seen designs that incorporate not only ovens, but also cook tops. The biggest drawback is expense, and since they are built in the home they can really only be used in cooler times of the year.
I was not familiar with aprovecho style cook stoves. After a little google time I just might have to readjust my thinking a little. These look very simple to use, and probably to build and look like they might be efficient too.