Though it isn't possible to know exactly which meaning to apply to a newbie who's first post is in the job section, OP can stand for any number of things, including Obvious Phoney.
There's a big difference between a "writer" (in particular, a published author) looking for an assistant and someone who simply wants to write a book.
This forum has had its fill of fake job offers. If the OP actually is a published author, it would make sense to provide at least a few (or at least one) of the "details" of the job: editing, writing descriptive passages or dialogue, and/or the entire book.