Due for release in May, Christopher L. Bennett will be returning to the TOS era with The Captain's Oath. Details beyond that are minimal at the moment, with just the tiniest preliminary blurb:
An all-new novel based upon Star Trek: The Original Series, featuring Captain James T. Kirk and the crew of the Starship Enterprise!Bennett also wrote the last TOS book to be published, The Face of the Unknown, and it seems this will be the first TOS book of the new year and new run of Star Trek novels after the recent hiatus, as the previously announced Greg Cox book, The Antares Maelstrom, has now been rescheduled, with an expected August release (instead of March).
In other books news, Blackstone have announced two more CD editions of recent Star Trek audiobooks (previously only available as downloads). April will bring us John Jackson Miller's Hell's Heart, the first book in the TNG-era crossover Prey trilogy. And then in May will be Dayton Ward's TNG novel Hearts and Mind. Both are read by Robert Petkoff and feature the same cover art as the previous download editions.
To keep track of all the latest releases, hit the prose or books buttons on my 2019 schedule page. You can also find series reading lists and author bibliographies on my dedicated Star Trek lists site.