Used book – Vampire Earth, Book 3: Legend of the Thunder, E.E. Knight

48th year of the Kurian Order. Alien vampires and their avatars, the Reapers, impose their bloody law on most of Earth, which has become their new hunting ground.

But the resistance has organized and is trying to overthrow the New World Order. David Valentine, a member of the Feline caste - the elite spies - has donned the enemy uniform to board the Thunder, an old gunboat. His mission: to acquire a weapon that was reportedly discovered in the Caribbean. A weapon capable of defeating the Reapers! If Valentine succeeds in this perilous journey, this 48th year of domination could well be the last...