A: It seems you're very busy recently.
B: Yeah. I have a sudden interest in philosophy and I'm digging into it these days.
e.g. Our shop, in fact, was just beginning to dig into the problem.
e.g. They digged into what was unknown in order to make it known.
e.g. He is digging into Chinese history.
have a interest in：对......感兴趣
e.g. We have a crucial interest in this topic.
e.g. They had a passing interest in music.