My kids are 12 years old, and I remember reading a book when I was that age which seemed the best science fiction book ever. It was about 1968 but I think the book was a few years old.
It had gorgeous colour templates of strange worlds in it. One scene had small cigar-shaped spaceships that dropped little cotton-wool-like objects. I think the author's name ended 'Clark'. Anyone know the name of the book?