A Russian immigrant who works in our office informs me that "marktvenovski"
is indeed a proper adjective, roughly translated as "in the style or manner
of Mark Twain." Thus, she indicates, it would be appropriate to refer to
"marktvenovski" humor, assuming the Russian you're speaking with has a bit
of "humor" in available vocabulary stores.
Martin Zehr
University of Saint Mary
Leavenworth, Kansas