Hide Book child pages from category

@gdz - I think we might need a little more information to be sure we understand the question correctly. I am a little confused about what you mean by "category".

Are you trying to hide the child pages from the outline block as shown in my screenshot?

One possibility would be to replace the outline with a view of chapter titles that link back to their content. 

I just tested and you can create a view of fields, showing only page titles and filter by depth to only get chapter titles. Something like this:

It does seem like there should be a better solution, but this my only idea right now. 

I hope I understood the question correctly.