The New International Biblical Commentary (NIBC) is among the better series of brief commentaries on the market. It typically employs well known scholars and is targeted towards lay people and pastors. If her section on Jonah is indicative of the entire volume, Achtemeier has given us a strong volume on the first six of the minor prophets. I found her writing to be clear, compact, and powerful. I found her commentary a great supplement to exegetical works, as her theological insight was keen. I especially enjoyed her comments on Jonah's prayer in Jonah 2:2-9.
This commentary will help you see the forest for the trees. Her explanations are grounded in what she sees as the major theological themes of Jonah, God's free grace and his love. While she focuses mainly on theology, there is some exegetical help, but it is limited.
Overall I greatly enjoyed this commentary. Even when I didn't agree with the exact conclusions she came to, she helped me wrestle with the theology of Jonah which makes the book a resounding success. I give it 5 stars out of 5.