Final answer:
The time dependency between writing a book and proofreading is Finish-to-Start (FS), where proofreading cannot begin until the book writing is complete.
Step-by-step explanation:
The time dependency that exists between the tasks of writing a book and proofreading is known as Finish-to-Start (FS). In a Finish-to-Start dependency, the proofreading task cannot commence until the writing of the book is complete. This is a common sequence in project management where the initiation of the dependent task (proofreading) is reliant on the completion of the preceding task (writing).