Write Moby Dick approximately

[dabos]

Can you tackle this one ? Short description:

Here is a 1.2Mb ASCII text file containing the text of Herman Melville's Moby-Dick; or, The Whale. Your task is to write a program or function (or class, etc. -- see below) which will be given this file one character at a time, and at each step must guess the next character.

If it tickles your fancy. Thanks.