There are 3 books in the The Imperials series. The newest book is The Hidden World which came out in 2019.

1
The High Ground

Book cover of The High Ground
In the Solar League, those without choice seek the High Ground … As humanity progresses through the stars, in some ways, it has regressed.The Solar League, under the control of its aristocracy, has conquered many races it has encountered, placing such aliens on the bottom rung of a social order…
When you buy books, we may earn a commission that helps keep our lights on (or join the rebellion as a member).

2
In Evil Times

Book cover of In Evil Times
An explosive new space opera from the Emmy Award-winning scriptwriter of Star Trek: The Next Generation

Thracius "Tracy" Belmanor and the Infanta Mercedes have graduated and become officers in the Orden de la Estrella. Tracy's posting leads him to doubt the intentions of the League, when he is required to…

3
The Hidden World

Book cover of The Hidden World
In The Darkness of Space Everything Hidden Will be Laid Bare …For fourteen years, Thracius "Tracy" Belmanor has struggled to make a life for himself after a betrayal had left him in military disgrace. Struggling as a captain of a small trading vessel, he survives with his alien crew under…