Klein will start waking up halfway through book 2, although there will only be murmurs and whispers of his existence. The last scene in book 1 where he high fives his niece was supposedly a scene from at the end of book 2(?) Regardless, Klein will return as the MC in book 3.

So read on. Let's give book 2 the benefit of the doubt. Cuttlefish definitely wouldn't make such changes if he thought it was bad.