Trump threatens to sue everybody and fails to carry through with most.
He is not a mentally stable man. Once you stop thinking of him as normal it is easy to see why he does these things and in fact you'll be able to predict his reactions to things. I don't think he is insane but he is not stable and has some problems that seem to have never been addressed. They are serious enough IMO to make him unsuitable and perhaps even dangerous as POTUS.
There will be a fly in Trump's ointment. The author recorded his interviews. Trump likes to throw around empty threats about suing this one and suing that one yet nothing ever comes from it. It's all adolescent bluster.
His hissy fit about the book only makes people want to read it more. I want to read it now too. So far, I haven't heard of any state secrets being revealed. Only people giving their opinion on Trump and he doesn't like what they have to say. He cannot tolerate any criticism. He is very thin skinned and insecure. He is also very childlike. He demands loyalty from people but doesn't show them any loyalty. What does he think is going to happen when he uses people like that and throws them under the bus? He seems to hire some very unstable people as well. It's a recipe for disaster.
When you hire people like Bannon, Scaramucci and Omarosa chaos will follow.