There are two good collections of Mark Twain's early travel letters that 
are fairly easy to find: Letters from Hawaii (the A. Grove Day collection) 
and Traveling with the Innocents Abroad. These, of course, cover his trip to 
Hawaii in 1866 and the Quaker City trip in 1867. But the Quaker City trip 
was only the final part of a journey he began at the end of 1866, in which 
he first traveled from San Francisco to Nicaragua, then crossed the isthmus 
and took another ship to New York. He spent several months in New York, with 
time out for a trip home to Missouri. As far as I can tell, the 26 letters 
he wrote between leaving San Francisco and departing on the Holy Land 
excursion have been published in book form exactly once, back in 1942, in an 
edition of only 1,795 copies. The title was Mark Twain's Travels with Mr. 
Brown (though in truth, Brown figures in only a handful of the letters).
  To my mind, the letters in this collection are even better than those in 
the other two books. They include a few stories from Ned Wakeman, who Twain 
met on this trip; his first published writing about Hannibal, including a 
mention of Jimmy Finn; a harrowing boat trip during which at least a 
half-dozen people died of cholera; and a lot of fine descriptions of scenes 
in postwar New York -- including a night Twain himself spent in jail, 
chatting with his fellow detainees. That's probably one story he never 
bothered to tell Livy.
  The letters are available at Barb Schmidt's terrific Twain Quotes site, 
but I have to wonder why the book hasn't been reprinted at some point in the 
last 70 years. It seems to me that such an excellent collection deserves to 
be more widely available.

-- Bob G.