A journey of self-discovery or a writer spinning out a plot?

Anything's possible in life, and if you can imagine it it's probably happened somewhere. And even more is possible in fiction - life led in reverse from old age to childhood, ghosts watching us from above and controlling fate, talking animals, benevolent dictators. That said, writers - at least writers of conventional literary fiction - have an obligation to stay within the bounds of credibility or, if challenging the boundaries, to convince us that we're in safe hands. What's going on with Vendela Vida's "Let the Northern Lights Erase Your Name"? From the start it was an improbable plot, but I've been willing to go along with her because her writing is quite good. But now, more than half-way through, I wonder about the book as a whole. Let's just start with the premise: a mother disappears, leaving behind 14-year-old daughter and mentally disabled son and loving husband. They never find her. On father's death, narrator, now 29, learns her mother had been married to a Finn and that he, ostensibly, is her father. Everyone else seemed to know this but not her (huh?). She goes off to Finland, finds her "father" by looking him up in the phonebook, and then he tells her that her mother had been raped by a Sami (i.e., Lapp) priest and that priest is her father. She, Clarissa, heads north to seek out the rapist/priest. Okay, so these are plot revelations, but hardly surprises and hardly credible outside the world of a writer's workshop. How could Clarissa be in the dark so long? Why did nobody search for her disappeared mother in Finland? How is it so easy for Clarissa to find these facts that have eluded everyone else? How does she afford this trip, by the way? I could go on - and I probably will finish the book (it's not that long), but is it really a journey of self-discovery, or a writer's inventing plot as she goes? And - judging from the adulatory blurbs from some major authors that I see on the jacket - I am really offending some literary gods by challenging Vida's creds, but come on, didn't anybody else find this well-written novel a huge stretch?