
It's very difficult to read, or form a coherent statement out of this. Try reading it left-to-right. Or starting at the upper-left corner, working your way down.
So the text in the upper left is meant to be an introductory summary and then each of the three coloured columns represents one of the three books, with the size of each block representing how many words each section of the story is and showing how much smaller thay are in the translations and how much relative space each section is given.
Can you think of any better way to represent that or should I just include text that explains all of that in the diagram itself?
Yeah, explaining the size correlation first would help a lot. For the translations I'd also take ALL the text out of the sections and have them instead in bubbles stacked on top of each other. At least for Makt Myrkranna this would help a reader's flow from the first chapter to the second, and it would feel more consistent.