While the novel and movie don't go into excessive detail about what kind of blood he drinks, we know he has a preference for human blood and specifically younger, innocent blood.
Here are some examples:
* He initially feeds on Claudia, a young girl he turned into a vampire.
* He also mentions enjoying the blood of young men.
* He feels remorse and disgust for feeding on older, more experienced people.
However, it's important to remember that the focus isn't on the specifics of his diet, but rather on the emotional and psychological impact of his vampiric existence.