The Bible was never meant to be read in order from cover to cover. If you understand the history of how the Bible was edited, you will see that the order has been changed many times over. In Jewish tradition, the five books of Moses (Gen. to Deut.) come first as the "Torah", then the books of the Prophets as the "Neviim", and then the books of Writings (i.e. Psalms, Proverbs, etc.) as the "Ketuvim". The first letters of the three parts of the Bible make up the Tanach, the Jewish name for what we Christians call the Old Testament. There are many books that overlap one another, for example, I and II Kings and I and II Chronicles talk about the same area, albeit with differences. If you studied the prophets, you will also understand that these people lived in the era of I and II Kings and I and II Chronicles. So it makes no sense just to read the Bible cover to cover thinking that everything has been laid out chronologically.

As for your questions regarding Lamentations, the people who laid out the scheduling of the reading may have forgotten about Jeremiah 52 because I can't find it in the online readings or are stating that Lamentations was written by Jeremaiah before he wrote Jeremiah 52. Whereby, reading Lamentations after Jeremiah 51 makes more sense in regards to his mental state and God's mind, then reading Lamentations after the entire book of Jeremiah.

FYI