I'm not sure if a lack of citations equates with Henderson being iced out,
but his work is not a biography in a strict sense, which may account for it
not being cited as often as other early biographical works. Henderson
himself called it an "interpretation" and perhaps "critical assessment" or
"critical biography" is closer to the Mark. Twain is discussed as a
philosopher, sociologist, humorist, moralist, and world-famous American
icon.

The book was published in the US from English sheets at the end of 1910, and
the English edition appeared March 9, 1911. Henderson had met Twain on one
of his trans-Atlantic crossings, and visitied him at Stormfield after having
a cordial correspondence with Paine, Isabel Lyon, and Ashcroft (I have
Henderson's original archive). It includes a useful bibliography of works
about Twain published between 1870 and September, 1910, and some great (and
now familiar) photographs (two in color) of Mark Twain by Alvin Coburn.

Kevin Mac Donnell
Austin TX