To Complex?

I have started the first chapter of Sweet Torture. It will be a two part book but instead of two parts contained in one book I am playing with the idea of making them two separate books with a book featuring another couple in-between that will contain a key element of Sweet Tortures story leading into part two. As a reader would that be irritating? Would it be to confusing to read part one, then a separate book altogether and then read part two? Or would it be good suspense? I don't want to give away to much obviously so I apologize if this is ambiguous but I am looking for opinions. What do you think?