The books were purchased after the deed was done.
A crime of passion can be covered up without making it premeditated.
That's one of the problems with all of the Reiser defenders: they are usually unaware to what degree Reiser has incriminated himself.
The guy strangled his wife. I don't think that's the kind of thing you premeditate. He's also a liar; I wouldn't read too much into his attempt to manipulate his later civil jury. The crime-of-passion narrative would still find for the plaintiff, so he made up some nonsense that the jury saw right through.
https://www.nbcnews.com/news/world/software-guru-ordered-pay...
"His defense essentially was that he killed his wife to protect his children from her."
That he made up different stories at different times is besides the point, the point is: you can't believe a word he says either way so any defense of a crime of passion is just as baseless as this one, though this one is actually much more believable and fits the evidence available. All of it points to a very smart guy who killed his wife because he thought he could get away with it but failed at that (and not for lack of trying) and who now thinks he can present himself as 'a changed man' when really he isn't.