Initial thoughts: The premise itself sounded pretty exciting — girl digs up the buried ashes of her late father in order to scatter them in Namibia, where she believes would be a much more significant resting place for him.
The promise of the Namibian setting especially drew me to the book. In the end, half the time Rhina was obsessing about her best friend and whether they could become more than friends. Yes, when someone falls head over heels for someone, that's all they can think about but really, in the case of Regenbogenasche, it completely detracted from what were much larger points of interest.
The prose itself was technically solid, though I didn't care for it. I think it was supposed to come across as poetic but to me it was pedantic. Even though the narrative was from the first-person perspective, there were a lot of third-person references to the main character. She often spoke of the persons (yes, plural) within her:
"Ich verweise die ganzen In-mir-Rhinas aus ihre Plätze und bitte einzig und allein die Charmante an die Oberfläche." (Translation: I expel all the within-me-Rhinas from their places and solely coax the charming one to the surface.)These are just a few examples of this stylistic prose. Once or twice would've been fine but to read this over and over again annoyed me somewhat.
"Dann rufe ich die Mutigen in mir zusammen [...]" (Translation: Then I call on the brave ones within me [...])
"Murrend erheben sich die Rebellen in mir." (Translation: Grumbling, the rebels within me gather.)
Also, I wish a greater proportion of the book would've been in Namibia itself than in Germany where all the preparations took place for the trip.
Despite my gripes, I did enjoy various parts of the book. Besides the explorations of Namibia, I also liked the unfolding her family history as Rhina was forced to reevaluate her identity and the memories of her father.