So I started the game last night and I read the Black Book The Winds of Change. I picked the ability Companion's Insight since I often travel with my wife Mjoll and I thought she might appreciate that.

Anyway I learned that there are more Black Books around. So my question is, if I pick an ability out of another Black Book will it override the Companion's Insight, or do we get to have one ability per book?

Thanks.

EDIT: Another question, is Companion's Insight a passive skill or do I need to 'turn it on' like a spell or something?

I can't answer the first bit, but check your Active Effects. I know Scholar's Insight is passive. Companion's might be too.

No it will not. There are 7 books total, and the books do not leave the inventory, cause you can go back and change what you picked.