You already own a phone, and it can display every book ever written, so why would anyone buy a separate gadget that only does one of the things a phone already does? It's a fair question, and the answer is more interesting than "the screen is nicer." It comes down to how the two screens work and, just as much, to what each device tempts you to do.
Two completely different screens
Your phone uses a backlit screen, a panel that shines light directly at your eyes, the same way a TV does. A dedicated e-reader uses electronic ink, a technology that reflects ambient light off the page the way paper does. It isn't shining at you. It's being lit by the room, like a real book.
That difference is the whole ballgame for comfort. E-ink looks matte and still, with no flicker and no glow. Many people find they can read it for hours without the tired, dried-out feeling a bright phone screen can cause, especially at night. It's also dead easy to read in direct sunlight, where a glossy phone screen turns into a mirror.
The distraction factor nobody mentions
The screen is only half of it. The other half is that your phone is a distraction machine. You sit down to read a chapter and a notification pulls you into email, then a message, then somehow you're watching a video. An e-reader does essentially nothing else. There's no app to check, no feed to scroll. That single-mindedness is the feature, even if it sounds like a limitation.
When the phone is the right answer
- You read in short bursts, a few pages here and there, and don't want to carry a second device.
- You read mostly in dark rooms and like an adjustable backlight, which both can do.
- You don't read enough for eye comfort to be a real issue.
When an e-reader is worth it
- You read for long stretches and your eyes feel it on a phone.
- You read outdoors or in bright light often.
- You want a device that lets you actually finish a book without interruptions.
If you read a few books a year, your phone is plenty. If you read a few a month, a dedicated e-reader pays for itself in comfort and in chapters you actually finish.