For concise summaries of features and options, nothing beats UNIX manual pages. This book doesn't cover every option and every feature (not even every command!) of MH. Some parts of the book -- like the Chapter on MH Formatting -- expect you to use the manual pages for reference.
Unfortunately, not all systems make manual pages available. To see whether your system has online manual pages for MH, try using the man(1) command to read the mh(1) manual page:
% man mh
If that doesn't work, try to find the manual page for the man command itself: type man man. Look for instructions on how to make man search directories other than the standard /usr/man tree. For instance, on my system, man looks at the directories listed in the MANPATH environment variable. Because my MH manual pages are in /usr/local/mh/man instead of the standard places, I've added a new definition of MANPATH to my shell's startup file:
csh, tcsh: edit .login:
setenv MANPATH /usr/man:/usr/local/mh/man
sh, ksh, bash: edit .profile:
MANPATH=/usr/man:/usr/local/mh/man
export MANPATH
If you make that change, re-read the startup file into your shell (type source .login or . .profile) and try the man command again.
Still can't find the manual pages? Ask your system administrator to install them from the MH source tree. If that isn't possible, you can get MH 6.8.3 documentation from SourceForge
If you're using nmh, get the latest distribution from http://download.savannah.nongnu.org/releases/nmh/. In the gzipped tar archive file, the rough manual pages are in the man subdirectory.
Now you're ready to take one (or more!) of the tours: