Worst. President. Ever.

Worst. President. Ever. flips the great presidential biography on its head, offering an enlightening—and highly entertaining!—account of poor James Buchanan’s presidency to prove once and for all that, well, few leaders could have done worse.

But author Robert Strauss does much more, leading readers out of Buchanan’s terrible term in office—meddling in the Dred Scott Supreme Court decision, exacer...