The title is Jeremiah's name: "Jeremiah." There, done—we can go home.
But we won't, because we want to point out how deeply the book goes into Jeremiah's character. His book's worthy of his name because it doesn't only record the prophecies ascribed to him; it also shows us something of the inner man. And the inner man is really despairing.
We really see Jeremiah's inner anguish—his fear of his persecutors, his wish to have never been born, his existential despair. It's all spelled out in painful detail. Where Isaiah retains an air of mystery (we don't know too much about his personal life), we see Jeremiah's experiences and struggles up close, from early childhood until sometime close to his death.