Isso soa como a duologia de Scott Westerfield (ou romance único, dependendo do seu mercado), Sucessão (título único) ou O Império Ressuscitado e O Assassinato dos Mundos (títulos inéditos individuais).
Da descrição da Wikipédia:
The novel is set in an undefined distant future (although it is implied to exist roughly 5000 years from now), in which there is a galactic empire spanning eighty worlds, amongst other human civilizations. The empire is ruled by the Risen Emperor, who has discovered the secret of immortality through means of a symbiont (spelled "symbiant" in the novel). Immortality is conferred on favored Imperial citizens, referred to as the 'grays'.
e também temos os personagens principais soldado e político:
The central characters are Captain Laurent Zai of the Imperial Navy, and Senator Nara Oxham, a member of the Secularist Party, which opposes worship of the Emperor and the use of the symbiont to create immortality. Despite their political differences, the two become lovers. Zai is sent away to fight the Rix; due to the death of the Emperor's sister at the hands of the Rix, Zai is expected to commit ritual suicide to mark his failure, but chooses not to do so. Senator Oxham, appointed to the Emperor's War Council, opposes unpalatable war plans that would lead to the sacrifice of billions of Imperial citizens in order to preserve state secrets contained in the compound intelligences.
E uma mulher guerreira de uma sociedade exclusivamente feminina também está lá ... na verdade, acabei de perceber que já respondi essa pergunta de você , aparentemente!