One of the most prevalent fan theories about Star Trek: Discovery concerns whether the series is set in the TOS era, or some new timeline that will be erased or altered before the series’ end. After reading the (excellent) first Discovery novel, Desperate Hours, I believe we have an answer. (Spoilers ahead for the book)
Desperate Hours is set aboard the Shenzhou and takes place about a year before the series premiere, “The Vulcan Hello.” The ship responds to a distress call from a Federation colony that’s being attacked by a massive alien juggernaut. At the same time, Michael Burnham is settling into her new role as first officer, while Saru is fuming because he was passed over for the role, despite his seniority.
After reviewing Shenzhou’s initial findings, Starfleet dispatches the Enterprise, under Captain Pike with orders to destroy the alien juggernaut at all costs, even the lives of the colonists. Georgiou and Pike square off in orbit. Meanwhile, Burnhan and Spock team up and explore the alien ship, giving them a chance to reconcile long-held animosities over their shared childhood under Sarek’s tutelage.
Throughout the book, author David Mack went out of his way to make it clear that Enterprise and Shenzhou coexisted, exactly as they appeared in The Original Series and Discovery. For example, the Enterprise crew wear their yellow/blue sweaters while the Shenzhou crew wear the uniforms we saw on the show. Only Shenzhou has holo-comms and a ready room. These and various other details make it very clear that Shenzhou and Enterprise are supposed to coexist in the prime timeline, and NOT some new timeline that’s going to be erased or overwritten.
It’s not hard evidence, but it seems unlikely that Mack would’ve written something inaccurate; especially given that one of the other Trek novelists, Kristen Beyer, is on the Discovery writing staff as a “go-between” between the show and its tie-in media. It would’ve been very easy to write this story without the Enterprise or the TOS references.
I personally don’t care whether they explain the differences between Discovery and TOS or not but, whatever the outcome of the series, it seems unlikely that the ending will involve more temporal shenanigans.