Immortality is not necessarily a good thing. At least as far as I know, this guy Aardman doesn't want to continue living. But the most troublesome thing for him is that even though he hates eternal life to death, he can't end his own life. As for the specific reason why this is so, we don't know, but when he laments alone, we can hear his longing for the past.
This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.