Twain was referring to ANNE OF GREEN GABLES. I have the quote in
a secondary source: The Dial, February 1986. It is the PBS guide
that just happened to be promoting both ANNE and the four-hour
HUCK FINN remake.
Clemens sent a copy of the book to Frances Nunnally in October
of 1908. See Gribben's MARK TWAIN's LIBRARY: A RECONSTRUCTION,
vol. I, pg. 480. In a letter to Francis Wilson, Clemens
states "In 'Anne of Green Gables' you will find the dearest
and most delightful child since the immortal Alice."
KB