This book was published by Olaf Stapledon
in 1947. It is evocative of his earlier, better known, and perhaps greater works Star Maker
and Last and First Men
The frame of the work is a letter from a man in an insane asylum to a scientist friend. He has made contact with a creature of pure energy. These creatures live most comfortably at temperatures to be found on the sun and other stars, but are capable of surviving dormant at normal earth temperatures, or remaining awake inside of a blaze produced by a good sized fireplace.
These energy creatures have great telepathic powers, and consider themselves to be of higher cultural development then humans. The letter writer is shocked and horrified to discover they tend to use their telepathic powers to prevent us from destroying ourselves, equating this almost to telepathic enslavement.
I won't give away the ending in case you wish to read it, but I will say these creatures are part of a galactic civilization such as in Star Maker which (unlike the earlier work) inexplicably goes through several stages of it's developement during a portion of the lifetime of a single man. Some of the ideas in here derive from his earlier work.
The text of this work is available online at http://www.geocities.com/Athens/Agora/7628/stapledon/the_flames.html