In a feat that even the best-selling writers might envy, young-adult author John Green's latest novel is No. 1 on Amazon.com and Barnes & Noble.com even though he's still working on it from his comfy La-Z-Boy in Indianapolis.

With "The Fault in Our Stars," the author has overtaken hot books by Suzanne Collins and Laura Hillenbrand. His book won't be published until the spring of next year.

It...