Why does the book of Jeremiah have the appearance of being a medley of unconnected passages which are sometimes in contradiction to each other for e.g. chapter 37:11-21 and chapter 38 are divergent accounts of one and the same course of events?

Part of your description is a reasonable assessment of Jeremiah, and part of it is simply mistaken.  About the content of Jeremiah being  “a medly of unconnected passages,” there is a grain of truth in this, although the description is unnecessarily negative. Let me explain.  Unlike Ezekiel, Isaiah and Daniel, the other three “major prophets”, Jeremiah does not have a clear order or chronology to its content.  It is fairly difficult to put a date to all of the prophecies in the book, but scholars agree that they are not chronological. The first 20 chapters come from his early career as a prophet, but Ch 21 and after are more random in their order.  There is some truth to the claim that the book is a “medly” 0f prophecies.  We do not know who put the prophecies of Jeremiah together in its final form, and we do not know the process chosen to put them into the order we have.  However, the second part of this criticism is not justified.  There is a clear connection between the different prophecies of Jeremiah.  I have taught a class on Jeremiah a number of times, and there are clear themes which run throughout the book.  I am attaching the notes from the class I have taught on Jeremiah.  Jeremiah Notes  You can see that there are clear themes which run throughout the book, and that Jeremiah does have a reasonable outline as well.

Here are the main themes of Jeremiah:

I. Admonitions against false religion

II. God’s judgment on his people and on the enemies of his people

III. Restoration of the remnant

The claim that Jeremiah contains contradictions is simply incorrect!  There is no justification for this claim whatsoever.  Your example does not support your conclusion!  To be honest, all you have to do is simply read the text (I am guessing that you did not, but that you found this criticism on-line). Jeremiah 37:11-21 and Jeremiah 38 are about two different events in which Jeremiah was persecuted by his enemies in Jerusalem. The first was a false accusation of him giving support to the enemy when he went to buy a piece of land during a lull in the fighting.  He did this to make a spiritual point, not to make money!  Jeremiah 38 is a second example of Jeremiah being persecuted.  This time it is for his actual prophecies, which were not what the king wanted to hear.  The causes of the two persecutions are completely different, and the nature of the two persecutions are also completely different.  Why would anyone claim that this is a contradiction?  Hmmm…  I assume you are reading a Muslim source.  Such sources are to be taken with a very big grain of salt or ought to be completely ignored, as they are not honest attempts at analyzing the Bible!

John Oakes