Well, apparently they were back then and still are today for people of all ages. People are making the adult coloring books bestsellers on Amazon! At the time of this writing, eight of the top twenty books on the bestsellers list, are coloring books for adults. There must be something behind this recent growth in interest.
Determine your childs level when it comes to coloring. Some color books provide large coloring spaces making it easier for children to color the page, stay in the lines, etc. As the child gets older, their skill level for coloring increases as well, and the difficulty of the book may as well. Some coloring books come with written instructions, and other games, such as a dot to dot, or a maze. If you want to keep your child happy, and still challenge them, choose coloring or activity books in their range or level, and do not frustrate them with books that have too small of pictures, or too many spaces to color, or written instructions.