So, what's the best way to dial down the speed in DosBox on the individual games. Specifically, Book 1 goes so fast that any message that doesn't involve a "Press Any Key to Continue" is invisible. (I'd never have known those gnomes were attacking if I hadn't checked the status screen.) I've tried mounting the folder to DosBox, but I can't seem to find the install files. Any help would be appreciated, thanks.

Use CTRL-F11 to reduce number CPU cycles. Notice the number when the speed feels right, quit the game, open the relevant .CONF file and edit it the new value for "cycles".

The relevant part of the CONF file looks something like this:
[cpu]
# core -- CPU Core used in emulation: normal,simple,dynamic,auto.
# auto switches from normal to dynamic if appropriate.
# cycles -- Amount of instructions DOSBox tries to emulate each millisecond.
# Setting this value too high results in sound dropouts and lags.
# You can also let DOSBox guess the correct value by setting it to max.
# The default setting (auto) switches to max if appropriate.
# cycleup -- Amount of cycles to increase/decrease with keycombo.
# cycledown Setting it lower than 100 will be a percentage.

core=auto
cycles=max
cycleup=500
cycledown=20

In this example you'd want to change "cycles=max" to the new number. That way you don't have to asjust the speed each time you start the game.

Actually, I don't recommend using the cycles setting. Instead, use this fan patch which lowers the speed in MM1:

http://www.gog.com/en/forum/might_and_magic_series/mm1_read_this_if_you_think_the_text_appears_too_fast/post38

Full thread for more info:

http://www.gog.com/en/forum/might_and_magic_series/mm1_read_this_if_you_think_the_text_appears_too_fast/page1

The reason this patch is better is that it only slows down the text, whereas lowering cycles will slow down the whole game. Also note there is an in-game delay setting which I recommend setting to 9, the highest.

MM1 is the only game with these speed problems, all the others should run fine without any patches or having to mess with cycles.