I thought that Kate came across more as a mother to Dexter than a wife. A nagging, helicopter, controlling mother. How many times did she mention the Lego??? Early on in the book she describes seeing her marriage in a more mature way: "clear-eyed with no illusions, no misconceptions, no shortage of disappointments, resentments, grievances". What???? That would make a great Hallmark card! At this point in the book, we learn that Dexter and Kate had been fighting because Ben got sick while Kate was away for work- -working because she could not accept (or enjoy?) staying at home with her children and manipulated her old boss into creating a new position for her. I can feel her impatience with Dexter. It made me uncomfortable to be a part of the way she treated him. In some ways, I understand Dexter's own withholdings. He is probably in constant fear of being berated, minimized, not quite good enough.
I think partners need to be able to accept the good and bad parts of one another, to be able to forgive one another for not being perfect, and to trust that each is doing the very best he/she can at the time. When the road is bumpy for one, the other needs to offer unconditional love and support- -believing in his/her partner until the other can believe in him/herself again.
(kimk, the trust was still missing in the first book as well. Although at the end, Kate seemed to still hold a softness for Dexter in her heart.)