Three or four rulebooks for a simple Eurogame! What's the point of fragmenting the rules in four different places???
Basically, it gives you two different versions of the main rulebook - one where the rules are explained in a narrative, play-by-example style, and another where the rules are explained in a more traditional, dryer manner.
The other items are a (single-sheet) game set-up guide, and a glossary/appendix booklet containing detailed explanations of every card and resource in the game, to help resolve rules issues... it's very similar to the one that comes with Le Havre.
Personally, I don't think the rules are particularly fragmented; I've found this division of content pretty sensible/easy to follow.