For those who don't know, Monsters! Monsters! (M!M!) is in fact using the Tunnels and Trolls rules system. It is not, however, using either of the two current editions (5.5 and 7.5 are both current editions), but it is based in earlier rules. Further, it's the 1st edition relayout, rather than the T&T 5th Ed compatible second edition.
The material inside can easily be used with 5th edition (simply use T&T 5th edition weapons tables), and includes some material that probably should have been in T&T 5th edition... namely, monster special abilities, and rules for oversized weapons. The Charisma rules are very different from those in T&T 5E and M!M! 2E. That said, it's a pretty good ruleset in itself, and provides the guidelines needed for 5th ed based play.
The scans are clean, but not OCR'ed. That's issue 1. It's the older rules edition is issue 2. Still, I recommend it.
[4 of 5 Stars!]