A new article, "Authors as Copyright Campaigners: Mark Twain's Legacy,"
by Catherine Seville, appears in
Journal of the Copyright Society of the USA (Vol 55, no's 2-3,
Winter-Spring 2008) , pp 283-360.
I haven't finished reading it yet, but it is very thorough and covers
Sam's involvement with copyright issues from early on in his career- re:
British editions of The Innocents Abroad- to his well-known testimony
concerning what became the 1909 Act, including his participation in the
Author's Copyright League (of Extraordinary Gentlemen? ;-) ) .