It really depends on the quality of the book / app. Anyone can do either. But doing either with a high quality bar is something else again. I’d probably say it’

It really depends on the quality of the book / app. Anyone can do either. But doing either with a high quality bar is something else again. I’d probably say it’s a tie. If I’m hiring, though, a high quality app beats a book hands down. A book doesn’t tell me much about your ability to actually build production software.