In some spiritual or occult practices, a possession book is a journal or notebook used to record information about spirits or entities that have taken possession of someone or something. This might include notes on the entity's behavior, characteristics, and any messages it may have communicated.
In the context of estate planning or asset management, a possession book can refer to a document or ledger that lists all of a person's assets, including financial accounts, real estate, and personal property. This is sometimes used to help heirs or executors settle an estate after the person's death.
In the context of bibliophilia, a possession book can refer to a book that has been marked or inscribed by a previous owner, particularly if that owner was someone famous or notable. Possession books can be of interest to collectors or researchers who want to trace the provenance of a particular volume.