Is Jonah a historical book or a parable?

In my assessment, the book is presented to us as a historical account. It is ascribed to a historical prophet (cf. 2 Kings 14:25), and it contains no authorial comments or literary clues that suggest it is a parable.

Nevertheless, some have questioned the historicity of the book, especially because of the miraculous events surrounding the fish. At times, the odd structure and ending of the book have been used to support this theory, since the book does not follow a normal form for historical narrative. And some have pointed out that the poem in chapter 2 cannot possibly be a historical account of Jonah's experience in the fish.

First, if we accept the reality of miracles, which I believe we must, there is no reason to think the basic events of the book could not have happened as stated. The book does not tell us whether or not Jonah died in the fish, although this is a possibility (Jon. 2:6). If he did die and return to life, it would correspond well with Jesus' mention of Jonah (Matt. 12:39-40). But in either case, divine intervention makes all things possible.

Second, the odd structure and ending of the book are actually good arguments against this book being a parable. The book is far longer than any other parable in Scripture, and it is cumbersome in its arrangement. Besides this, it names an actual historical figure as its main character. All of these facts point away from Jonah being a parable.

Third, the poem in chapter 2 does appear to be a later rendering of Jonah's experience in the fish. Probably this is a poetic summary of Jonah's fear and panic in the fish, and of a vow he made to the Lord for salvation from the fish. It is likely that this poem was composed to attend the payment of the vow upon Jonah's return to Israel. This does not cast any doubt on the historicity of the events portrayed in the poem.

Finally, Jesus indicated that his death, burial and resurrection would take place "just as Jonah became a sign to the Ninevites" (Luke 11:30). He also indicated that on the Day of Judgment the Ninevites would condemn the unbelievers of Jesus' generation (Luke 11:32). Both of these details especially the second indicate that Jesus believed that the story of Jonah was historical. This alone ought to convince us of the historicity of Jonah.

Other interpretations of Jonah have also been offered, such as it being either allegory or midrash. With regard to allegory, there are no textual cues that it is an allegory, and Jesus did not treat it as such. Moreover, if it is an allegory, most of its details are far from intuitive, so that it would be a highly unusual and indeed rather useless allegory.

Midrash (essentially an expository commentary on other Scripture; cf. Jon. 4:2) is a possibility, although the book of Jonah contains far too many extraneous elements for it to be simply a commentary on Exodus 34:6-7 or the various psalms and such alluded to in chapter 2. And again, Jesus' treatment of the book as historical argues against this reading.

I think we have to conclude that the story told by the book of Jonah is historical.