This is definitely a classic, in some ways similar to Kafka's Hunger Artist, which I think is more social commentary while Hamsun's book is more interior psychology oriented. In any case, you won't find anything like either one nowadays as both talk about social-personal attitudes that we prefer not to think about and talk about them in a way we no longer permit ourselves. In view of the human fates involved in our approach to climate change and the recent concatenation of unexpected human events, it might help your understanding to read Hunger and the Hunger Artist. In any event, Hunger is a great read.