I asked around a bit. Do you remember this book the protagonist of Your Lie in April was reading in the fifth episode?
I’d mistaken it for The Little Prince, but my informants tell me that it’s actually Usotsuki no tensai (The Genius Liar) by Ulf Stark. It doesn’t appear to have ever had an English translation, so I’m not certain what the thematic significance of the book is, but the title suggests that the book was deliberately chosen to convey, well, something. I’ll do some more digging and see if I can find out more.