The whole thing was utterly disjointed.

There isn't even decent continuity within individual paragraphs, for fuck's sake.

Anti-fan theory: The story is written from Eragon's perspective, as the eldunari progressively mess with more and more of his mind and perception, so the gradual decent into incoherency throughout the series is a reflection of his mind and memories straining under the pressure of so many hastily-patched modifications by the eldunari

But of course if Paolini did that intentionally it would be orders of magnitude less subtle.