"When you find a wizard spell of 1st level or higher, you can add it to your spellbook if it is of a spell level you can prepare and if you can spare the time to decipher and copy it."
"You determine what spells you know and can prepare for each class individually, as if you were a single-classed member of that class."
Brrr. That would be a drag. So then adding your spell casting levels from two mult classed spell casters only gives you higher level spell slots to allow you to upcast the lower level spells? Maybe this is what Larian was referring to when the talked about giving access to higher level spells than normal. One can hope.
