I purchased this RPG because it was a very early RPG (an antique), but I find the Mesoamerican style setting to be very interesting.
The system seems fairly straightforward, but the power curve seems different than I'm used to; Priests and Magic Users seem to be exceedingly limited in their abilities, both in quantity and power of spells. A lot of spells are once per day, ten minutes tops, and you don't seem to get very many spells, even at higher levels.
The scales (from its wargaming roots, I assume) can get confusing sometimes, especially for the spells, when they switch between dungeon and and actual measurements; it took me a while to figure out the three inch light spell had a thirty foot range.
It's definitely very combat focused, and full of random encounter/treasure/event tables, which seems to have been common back then. Not necessarily a bad thing, but it does seem to make it fairly focused on dungeon crawling.
I find the descriptions for some of the random events and artifacts to be rather interesting, but perhaps that's just me.
The foreward by Gary Gygax, and the TSR catalog (Dungeons & Dragons Basic Set; $10!) in the back made me very nostalgic for a time that before I was born.
Overall, I don't know that I have much opportunity to play this, but it's an interesting setting and it was an interesting read. I'm happy I bought it.