Scarlett Thomas writing for The Independent calls Parallel Worlds "absolutely impossible to put down." Mark Mortimer for Universe Today felt the book maintains a nice balance between detail and corollary while sometimes drifting to the philosophical side of things. Gerry Gilmore of the Institute of Astronomy, wrote that the book "is not a classic, but does raise many interesting ideas." Gilmore praised the book for its "exotic physics" and felt there were "lots of intellectual challenge" but believed there "was a little too much of a pot-pourri." Gilmore wrote that the biggest weakness of the book is how it covers astrophysical history.