With regard to the personal life of Obadiah, information is lacking. His prophecy was probably delivered about the time of the fall of Jerusalem, b.c. 586. It is the shortest of the prophetical writings, containing but twenty-one verses. Its theme is the doom of Edom, because that nation mocked Jerusalem when the latter was destroyed. Its predictions have been completely fulfilled. - Through the Bible Day by Day
The Doom of Edom

I. The Destruction of the Nation, Obadiah 1-9
II. Edom’s Heartlessness toward Israel, Obadiah 10-16
III. Israel’s Exaltation, Obadiah 17-21 - Through the Bible Day by Day