The book begins and ends with the same phrase, repeated 6 times: “I will…”
In the beginning, the Lord is promising “I will…” in regards to destruction. In the end, the Lord is promising “I will…” in regards to restoration.
In 1:12, the Lord punishes complacency. That’s one reason I’m so fearful of growing complacent. See also Matthew 25 and the parable of the unfaithful steward.
In 1:15-16 we see the day of the Lord again (as in Joel). Again, it is not a pretty day. No sunshine and roses.
In 2:11, it is worth noting that everyone from every nation bows down to Him. So does every god. Perhaps it would be good to do before you see His mighty destruction as 2:1-3 suggests.
A good verse to memorize would be 3:17. It’s comforting really.
Note: I remember reading this book back in Bible college about 6 years ago, and I remember circling all those “I will”s at the beginning and end. I also remember memorizing 3:17. I’m glad the Holy Spirit aids our memory.