Sherlock, the "Murder By The Book"/"Most Crucial Game" house is the one I was talking about before -- it was also in "Prescription: Murder". You'll find a whole discussion of that house in the Scrapbook article, "Columbo Flashback". It's called Stahl House.
The mansion used in "Etude In Black" is the same mansion seen in "Benson" and if I'm remembering correctly, it is also the house used in "Fresh Prince Of Bel Aire". That house pops up a lot in TV shows and movies. However, it is NOT the same house as Jarvis Goodland's in "Greenhouse Jungle". I myself made that mistake but then I looked at it closer. The Goodland house is not the same as the Bennidict house. They do look alike however.