Impractical for DMs by modern gaming standards, but undeniably cool artifact of the game as the pioneers played it...
This is more something you get for the collectible value and basic weirdness of it than it is something you want to break out and use as a DM all the time in terms of treasure summaries or adding interest to treasure hauls. I can see using pieces of it here and there, but there are really just pages and pages of monsters sorted by encounter area and rarity as well.