If Mark Twain was the Abraham Lincoln of American literature, then Lincoln was the Twain of American politics. So says Fred Kaplan, distinguished professor emeritus of English at Queens College and the CUNY Graduate Center, who has written biographies on both men. His new book, “Lincoln: The Biography of a Writer,” has been generating attention, in this bicentennial year of Lincoln’s birth. Just months before his inauguration, President Obama was photographed by the Associated Press holding a copy of the book. Prof. Kaplan discusses how he seized an unprecedented opportunity to “look into the origin and development of Lincoln’s genius with language, especially since I saw that no one else had done that before.”