A franchise novel based almost entirely around a character who appears only in one episode has to be really good to meet this mark. 'The Never Ending Sacrifice' meets that mark.
It follows the life of Rugal, a Cardassian boy brought up by a loving Bajoran couple who adopt him during the Occupation. When they visit Deep Space 9, the commanding officer decides that Rugal's interests would be best served by returning him to Cardassia with his biological father who had been tricked in believing Rugal was dead (Cardassian feuds and politics can get really nasty).
That decision is to change Rugal's life, landing him on a strange world among a people he regards as enemies.
The title of the book refers to a classic Cardassian novel which looks at the demands Cardassia makes of its citizens, again and again. Service to the state is part of the culture, spontaneous help to your fellow citizens is not.
The culture on Cardassia is well developed, with lots of subtle detail to make it totally believable. As Cardassia becomes involved in war after war, betrayal after betrayal, its citizens as well as Rugal continue to make sacrifice after sacrifice.
This is not an easy book, or a happy one, yet a few good things do do emerge. Rugal's background leads him to question and mistrust everything is he is told and to develop his own philosophy of life. His ability to relate to people from other cultures and backgrounds gives him a flexibility that most Cardassians lack and will lead him to some genuine friendships.
The characters are well-drawn, particularly Rugal's grandmother who despises him, but whom he comes to love and loathe in equal measure. This entry was originally posted on Dreamwidth where it has comments.