The book of Lamentations is very closely associated with the book of Jeremiah, as they both deal with the destruction of Jerusalem: Jeremiah as a prophetical warning, Lamentations as a lament after the fall. The poetry is important in interpreting the book as it highly corresponds to the message, which is that although the people have turned away from God, and have been punished as a result, they can still confess their sin, and receive His blessing once again.

Read more about the book here.