Legal Question in Criminal Law in California

Your question isn't very clear. If you're asking whether an author's admission of a crime is somehow privileged because it is contained in a book, the answer is no. At the same time, there are limits on when and how unsworn, out-of-court statements may be used as evidence. Those limits apply to admissions made in books just as they do to any other such admissions.

There may be other reasons why the crime would not be prosecuted. For example, if the crime was committed long ago (you mentioned a period of 40 years), the applicable limitations period may have long since expired.

If you admit to a crime, or provide facts that could lead police to determine it was you that committed a crime, and the statute of limitations has not run on it, you could face charges. There is no 'privilege' available, except to confession to a Catholic priest.