Xteink's credit-card-sized X4 Pro e-reader is $10 off for October Prime Day, bringing it down to $89.
Xteink, the Chinese startup behind last year's original X4 pocket e-reader, followed it up with the X4 Pro: same tiny footprint, but with a temperature-adjustable front light, a touchscreen, a faster processor, and more memory. It doesn't carry an official "Prime Deal" badge, but it's still discounted from its usual $99. At $89, it's likely the cheapest e-reader on sale right now that has both a light and a touchscreen. Even at full price, it undercuts the entry-level Kindle by $50.
The real selling point isn't the spec bump, it's the size. A device small enough to disappear into a pocket is more useful day to day than a bigger screen with more features you won't use. The catch is that it won't load your existing Kindle library, so you're on your own sourcing DRM-free ebooks.
That tradeoff makes this a niche pick, not a Kindle replacement, more a novelty for readers willing to work around Amazon's ecosystem than a mainstream upgrade.