I absolutely adore DQ, and played in a years-long campaign of it in high school. It was probably about as popular as Chivalry & Sorcery, etc. back in the day, a distant fourth or fifth place to D&D, RQ, and T&T.
The book was originally a boxed three-book set, then was published in a single softcover edition, and later, the TSR blue cover removed the whole section about demons.
A trove of magazine articles were published about it, many appearing in Dragon, including things like: Hunting/Fishing rules, the Warrior alternative class, the College of White Magics, improved social backgrounds, Horsemanship, some magic rebalancing, etc.
The D&D/DQ hybrid adventure also included a new magic college... Shaping Magics, if I recall correctly.
Universe, however, was loosely based on the DQ rules, IIRC. Unfortunately, word is that it was written by someone who'd never actually played an RPG (I am not sure about that, but is very believable), and the rules are an overcomplicated mess. I've got a copy, tried to run it, but we gave up at the end of the first session of character creation and a sample combat. This was remarkable, as we were veterans of games like Ysgarth and the Tri-Tac System games, and were pretty adept with DQ.