If you are interested in monster lore, rather than simply stats, I would strongly recommend getting Monster Manuals from 2nd edition AD&D. The 2nd edition Monster Manuals all include sections on Activity Cycles, Diet, Environment and Ecology of the various creatures presented.
They also include information on what kind of organization they are likely to be encountered in (ex. Dragons tend to be solitary, Goblins tend to be in clans of 10-40, etc.) The environment and ecology sections give you an idea of where you might find the creature, but also of what it does in that environment, whether it be a herd animal, an apex predator or an unholy abomination that has no place in any natural order.
From my experience with the other editions, all the rest have similar levels of detail to what is found in 5th edition. Acceptable, but not nearly as obsessive as 2nd editions was.