Is it permissible to compensate for the value of a book whose CD was taken without permission, by purchasing items of the same value from the bookstore, given that a long period has passed since the incident, out of fear of the officials' reaction if they are informed of what happened?

What was taken from the library must be returned. If it is not possible to return its like, then its value should be returned. There is no harm in doing so without the knowledge of those in charge if there is a fear of harm resulting from their knowledge. Repentance consists of regretting sins, abandoning them, resolving not to return to them, and returning rights to their owners or seeking their forgiveness.