up of single
digits corresponding to all but the last digit in the filename. For
example an eBook of filename 10234 would be found at:

http://www.gutenberg.net/1/0/2/3/10234

or filename 24689 would be found at:
http://www.gutenberg.net/2/4/6/8/24689

An alternative method of locating eBooks:
http://www.gutenberg.net/GUTINDEX.ALL