Yes, the “Atronach” perk in The Elder Scrolls V: Skyrim does stack with magic resistance. Here is a detailed breakdown of how these effects work together:

1. Magic Absorption: The Atronach perk from the Alteration skill provides 30% permanent Spell Absorption, which means there is a 30% chance to completely nullify the effects of hostile spells and add the casting cost of the spell to your Magicka.

2. Magic Resistance: Magic Resistance decreases the damage of any offensive spell by the displayed percentage. The total Magic Resistance is capped at 85%, and stacking is possible.

3. Stacking: Since Magic Absorption and Magic Resistance are two separate effects, they do stack. The game first checks if the effect is absorbed, and if that fails, it then applies the Magic Resistance.

In summary, if you have the Atronach perk and also have some level of Magic Resistance, the spell will first be checked for absorption. If it is absorbed, the spell’s effects will be negated, and if not, the Magic Resistance will reduce the damage from the spell. This means that having both effects will provide additional protection against magical attacks.