The illustrations, while primitive, are very charming. I can see these being easily copied by elementary school students, who could do their own versions of Stick Dog, encouraging creativity.
This series would be my number one pick to take on a long car ride if I had a children between the ages of 4 and 18. Unlike Wimpy Kid books, which are full of middle school themes, these appeal to the younger readers while still being amusing enough for parents, with some jokes that first graders wouldn't get. Since it's not essential to read the books in order, these could be passed around so that everyone could read them, or they could be read aloud, as long as the person in the passenger seat doesn't get car sick!
And of course, it might be necessary to stop for ice cream at the end of the book...