Good observation. This looks like reported speech - i.e. the language of one of King's characters. Stephen King writes perfect English, but he also writes well-observed characters, including their 'native' speech patterns. Many native speakers get this kind of construction 'wrong', certainly in Estuarine English you will find all of the following, quite commonly:
1 Me and my sister went to see mum.
2 They brought a bottle of wine for my wife and I.
3 Can I take some details from yourself?
1 Object pronoun for a subject; this is your King example
2 Subject pronoun for an object.
3 Using the reflexive in place.of.the object pronoun. Telesales and customer services agents often use this on the phone, I think as a way.of.trying to be polite. It doesn't work with me.
Declension of pronouns is a tiny, obscure part of English which is a relic of the language's history. Many native speakers don't really acquire a sense of case as small children, and it is no longer taught in schools, at least in the UK, hence the muddle.