Admittedly, as the last book in the Old Testament, and a minor prophet at that, Malachi is often overlooked by Bible readers. Yet, Malachi's passionate proclamations and the significance of what he had to say to his people capture the attention of even the casual reader. The message of Malachi came at a time of cultural and religious rethinking for Israel (roughly 500 B.C.E), when God's people were scattered throughout the Near East, with most living in Mesopotamia under Persian rule. They could easily have disappeared from history had it not been for the prophetic call to repentance.
In his fresh new translation, notes, and comments on this brief prophetic book, Andrew E. Hill explains why we should pay attention to Malachi as God's spokesperson. Hill places the book in its historical context to interpret the original meaning, as well as offer the modern reader insights into what it has to say to us today. With a wonderful insert filled with photographs, line art, and maps, he provides all the necessary details for the reader to understand and appreciate Malachi.
A very thorough commentary covering a very short book. Hill's commentary is exhaustive but not dry. He looks extensively at the Ancient Near East Backgrounds, biblical language, literary and critical contexts.
If you don't have all the time or money for this commentary, I'd recommend Hill's short commentary on Malachi in the Tyndale Old Testament Commentary series.
The most thorough study of Malachi, but not quite the best. Excellent exegetical insights, but it usually fails to synthesize the atomized readings and present them as a unified piece of literature, i.e. Malachi.