The anime for overlord while having being worked on by one of the best animation studios. isn't perfect. The anime skips alot of the source material in the first season while in the second they stay more true to the source material but they don't include everything from it, as a perfect adaption would.

Animation wise, it's ok. Most of the scenes are either single a frame with barely any animation on it, especially the scenes with creatures without mouth movements. Or they are heavily animated scenes where even the fabric of clothing is being animated. This would be a good animation quality from any other studio but from madhouse, one of the best. You'd always expect to see living scenery and not still frames with barely any life in them.

If you read the light novel, aka the source material. You'd know the story already and you wouldn't be missing out any details other than seeing the animated form of the scenes from the book. If you haven't read the light novel though you'd be lost about certain thing here and there, like why did ainz decide to use ____ kinda punishment? or does ___ have any brothers/ sisters? or how did ___ find ____ ? and etc. You'd honestly be lost in those finer details as the anime does skip alot of the explanations for things and doesn't go into what each character is thinking, unlike the Light Novel.

As long as you read the light novels alongside the anime, you should be fine. But if you don't you'll get confused here and there. It's still enjoyable regardless though. So, I highly recommend it a watch.