Hmmm, I would probably impart to them the basics and divulge more on case by case basis as they gain more levels.
For example, a low-level Ranger might get, "You recognize the creature as Y, an otherworldy abombination," whereas if a mid-level Ranger found a clue, "You recognize X clue as indication of Ys in the area, an otherwordly creature from Z," whereas a high-level Ranger would likely get almost all relevant info from the entry, including any strengths and weaknesses.
Sometimes a low-level Ranger might get mid-level info or mid-level might get high-level info depending on the situation, like if they'd fought one before or were seeking one as part of a mission (basically, a reason to have studied them more specifically during training).
If a more generous ruling seems to heighten the excitement of the moment or if the player did something creative as part of the inquiry, I would probably also lean toward more over less. I generally enjoy a chance to let a PC's special ability shine.