Stephen Hawking's "ultimate book" due out in September

Theoretical physicist Stephen Hawking, author of the 1988 best-seller
A Brief History of Time, is due to publish his first book since 2001's
The Universe in a Nutshell, announced publishing blog GalleyCat on June 28.
The Grand Design will be out internationally in September.

Hawking's latest title is co-written with Leonard Mlodinow, a physicist at the California Institue of Technology and author of The Drunkard's Walk: How Randomness Rules Our Lives. Mlodinow previously collaborated with Hawking on the 2005 book A Briefer History of Time, an abridged and updated version of Hawking's best-known title.

GalleyCat quotes a statement from the book's US publisher, Bantam Dell: "Drawing on forty years of Hawking's own research and a recent series of extraordinary astronomical observations and theoretical breakthroughs, Hawking and Mlodinow examine the evidence for the existence of a 'unified theory'-a single theory that can describe and explain all the forces of nature."

When introducing the book at BookExpo America 2010 in May, Jennifer Hershey of Ballantine Bantam Dell called the title Hawking's "ultimate book" and said it would tackle questions such as "Why do we exist?" and other key hows and whys of the universe.

Especially known for his work on theories about the Big Bang and black holes, Stephen Hawking is the author of a handful of books written for the general public. His runaway international bestseller A Brief History of Time remained on bestseller lists for years and has sold ten million copies worldwide.

The Grand Design will be released on September 7 in the US and on September 9 in the UK.