Of all the headaches of her current book tour — the declining sales, the constant travel, the interviews that generated unkind headlines about her family’s wealth — this one may sting Hillary Rodham Clinton the most: Her memoir, “Hard Choices,” has just been toppled from its spot on the best-seller list by a sensational Clinton account by her longtime antagonist Edward Klein.

It is a powerful statement about today’s publishing realities that Mr. Klein’s book, a 320-page unauthorized and barely sourced account full of implausible passages, including one about a physical altercation between Mrs. Clinton and President Obama, has landed atop the New York Times best-seller list, knocking “Hard Choices” to No. 2.