Looking for a children’s book-series (i remember three books – maybe there were more of them), with many illustrations.I read them at school library in South Africa around 1980/1981. The style the peoples were illustrated was sort of like Mick Inkpen-style. And it was always about to boys/young men. And after some thoughts it dawned to me, that the books seem to have described economical or political situations for children, worked into some fantastic stories. Here some of the contents/pictured scenes I remember:

One book was called something like ‘the lemonade bubble’ or ‘yellow soda bubble’, and was about producing lemonade in small scale at first, the production getting bigger and bigger with more profit and getting out of hand in the end, so that the market was drowned with too much yellow lemonade. Something like that. 

The second book contained something about posters showing some face maybe (?), glued to every wall in the town. And in the end of the story they invented a dragon-machine-truck, that ripped the posters off the walls, mixing it with different colours and spraying the paint back on the wall, thus making the town colourful again. It could be about elections or something like that?

Of the third book I remember little, but I know it was about a dispute among the two guys, and how they each set up a frontier/border and patrolling it, spying each other and so on.

The special thing of these books were the illustrations on the inside of the hardcovers – they showed how the main figures (two boys or young men?) ‘came into and left’ the book. In one book they came with an hot-air balloon (getting stuck on a church steeple)and left the book again with some sort of flying steps (taking one step from the bottom and adding it to the top – and this way climbing higher and away), in the next book they arrived with these steps and left through some underground tunnel, chasing a yellow butterfly. In the next book coming through the tunnels and leaving by some other way . . . and so on.