I spent five years writing my second book on game development. It sold three copies since last summer.
Wow, I'm really sorry, I know the feeling. Just feels so bad when you see others succeed with way less effort. BTW, I checked out your book about interpreters, it looks pretty cool, I was also obsessed with my own scripting language for a while, even got it to run from NFC tags lol. Your 'portfolio' also looks pretty nice in general. Are you also Romanian by chance?
Ti-ai scris numele pe coperta asta, am banuit ca esti roman. Eu sunt din Oradea, mult succes!