I don’t think the book has any furigana (or hardly any), so I think to not get frustrated by too many unknown kanji, maybe level 30 or 40 is advisable? It also depends on your tolerance for word lookups, and whether you read paperback or ebook.
Another big factor not reflected by your WaniKani level is your grammar knowledge. Since the book is aimed at adult readers, and since we‘re reading 40-50 pages a week, I would say at least N3 or N2? Of course that’s also dependent on your pain tolerance for unknown grammar (which is harder to recognize and lookup than vocabulary) and the amount of time you’re willing to put into this.
If you‘re not that confident yet maybe check out one of the Intermediate or Beginner Book Club picks first? We’ve read books with full furigana before as well, so you’re less dependent on your kanji knowledge.