The Last Werewolf (The Last Werewolf #1)

Meet Jake. A bit on the elderly side (he turns 201 in March), but you'd never suspect it. Nonstop sex and exercise will do that for you--and a diet with lots of animal protein. Jake is a werewolf, and after the unfortunate and violent death of his one contemporary, he is now the last of his species. Although he is physically healthy, Jake is deeply distraught and lonely. 

Jake's depression has carried him to the point where he is actually contemplating suicide--even if it means terminating a legend thousands of years old. It would seem to be easy enough for him to end everything. But for very different reasons there are two dangerous groups pursuing him who will stop at nothing to keep him alive.