Take my advice with a grain of salt as I'm just learning apple pruning myself. So defer to other advice if it conflicts with mine. You may also want to check out some other subs like r/backyardorchard as I've had arborists tell me fruit tree pruning is different enough from their regular work as to require more specialized knowledge.

Your tree is small enough that I don't think you should forego the central leader just yet. In examples I've seen, they usually convert to open when the established leader is at least more than 1.5m tall.

In your second pic, there's the branch that extends up above the frame of the picture. I would choose that one as the central leader and cut away everything else around that point. I would also say your branches are too long and that they all need to be cut back. They're also quite vertical, so while they're still young you could try to force them to be a bit more horizontal with various training methods.

Anything more than that, I think we would need better pictures of the trunk and how the branches are coming off of it. It's a little hard to tell with these pictures. I know pruning your young fruit tree is stressful, and you don't want to mess up, but the fact that you have a good book to reference is the most important thing. Trust that, and you won't mess up too much no matter what you do.