The Captain's Oath. The book is a TOS prequel, focusing on Captain Kirk taking command of the Enterprise, and his missions on his previous command leading up to that.
Various previews have now been released, which you can check out below. Starting with a reminder of blurb, as it appears on the back cover:
Here's an excerpt from the book, care of Amazon Kindle. You can read the prologue and chapter one:
The book also has an audio edition, read by Robert Petkoff. The cover is a slightly expanded version of the text edition:
Here's an audio excerpt too:
As a cool little behind the scenes feature, StarTrek.com have also posted a video showing Petkoff recording some of the audio edition.
Speaking of extra features, Bennett always releases extensive annotations for his books, and those for The Captain's Oath are already online. You can get insights into every little reference in the book from there.
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.