I love World of Carbon (and it's companion volume, World of Nitrogen)! I've been trying to get the rights to republish both with modern annotations, but I'm apparently not a big enough publisher for William Morris Endeavor (literary management for Asimov's estate) to respond to. It's sad, since both books are out of print.
His scientific writings for lay people are amazing(World of Carbon comes to mind). He could string everything together so well.