Again Nyom, and it's good to ask to get 100% clear, since acting on doubt is akusala in any case (defuse, moha).
If one has gained possession on something, hold something as own, perceives it as own, yet gives it as gift, such is kusala.
If one does not own something, perceives it as somebody else, when taking on it without being given, that is taken what is not given, such is akusala.
And it would be still akusala if thinking "I take what is not given to give".
But yes, and that is why Atma nevertheless talks on. Doing something based on doubt is also akusala.
So again: Nyoms parents have died. They left their things behind for their children. Has Nyom any clear perception that the book was unrightly obtained by her parents. Is the book now Nyoms book? And does she not actually perceive "this has been given by the goodness of the Sangha, has been given by the goodness of my parents"?