Is it a _% chance to avoid and absorb all spell effects? A _% of mana and damage that is always absorbed from every spell that hits you or does it just absorb the mana used to cast the spell but still do damage to you?

Its a chance to fully absorb a single spell attack against you, unlike resistance which resists a % of every spell damage, spell absorption fully resists one out of some spells that hits you, so the percent chance you have enchanted is the percent of spells that you will fully absorb, so for example 20% will absorb 1 in 5 spells that hit you.

Absorbs will also negate additional effects, such as getting slowed my frost spells, if the absorb is succesful. Normal magic resistance won't do that.

Sadly, absorbs are bugged somewhat. It'll stop some of your own spells from working, such as summons, the nightingale drain spell and others.

it's also a flat % caps at 80% and is all or nothing. so you never absorb 80% of a spell you either take it all, or nothing at all.

It's all or nothing, and caps at 80% absorption. so 20% of the time you're just going to get hit.

Does anyone know if the amount of magic resistance you have effects how much you absorb? Does having less resistance mean you absorb more magicka due to the fact that the spells inflict more damage on you?

In other words, do you absorb the same amount of magicka from spells with 85% magic resistance as you do with 0%?

The game first checks for absorb magic and only if the check is not successful then it checks for resist magic.