By the end of the book, Habakkuk is a changed person-he has learned to wait and trust in God, who works out all things for his glory. Habakkuk, like Job, questions God’s justice, but in the end both realize that God is sovereign and his justice is far beyond their comprehension.
1.2-11 First cycle. Habakkuk is disappointed that God does not seem to be answering his prayers; but God’s response indicates that unknown to the prophet, he has already begun answering them.
from ESV Study Bible, notes on Habakkuk