The Book of Joel

Joel is a short book with apocalyptic themes.  It speaks of locust swarms, armies invading, the sun turning to darkness, and the moon to blood.

Taken literally, a lot of this sounds melancholy, but the text itself supports that some of the imagery must at least be metaphorical.  For instance, the locusts eat "years".  Locusts do not physically eat large intervals of time, but rather grains.  So, the context seems to refer to a restoration of the loss of time.  But what are these "locusts"?  What "years"?  The passage does not explain, but leaves its interpretation mysterious.

The only other thing that stand out with Joel is that 2:28 is referred to by the Apostle Peter as a prediction of the events at Pentecost.  So, this would suggest that Joel in some part predicts the ministry of Christ.