Although this doesn't respond specifically to Twain's influence on modern writers, it is an interesting bit of trivia. I once sent a letter to Larry McMurtry, a copy of a letter that Twain wrote actually, in which he apologized to the county clerk of Archer County Texas for late payment on the taxes of land he owned there. As I remember, Twain said that if he ever ran into the agent who was supposed to pay the taxes on his behalf, that agent would "beg for brimstone, and he would beg in vain." I sent it to McMurtry to show him that he was not the only famous author to have owned land in Archer County. McMurtry wrote back and said that he was glad to know it, and that he would check to see if they owned some of the same land. I guess they didn't since he never wrote back. But I found it an interesting fact, nonetheless. What about Kurt Vonnegut? I haven't seen anyone mention his works. His essays, particularly, have been influenced by Twain's wit.