There is nothing in the e-Ink tablet space that can render high resolution PDFs and image files?
It's been a few years since I tried a e-Ink device, it was pretty mediocre back then. However, I would have thought that by now e-Ink devices would have no issues with performance.
Onyx Boox makes pretty nice devices that (from what I've read in reviews) have no problem rendering pdfs or running most android apps you chuck at them.
Cons: using demanding apps drains battery at the rate you'd expect of a tablet, not a dumb e-reader, plus they're expensive.
The Onyx Boox is an interesting device. Although where I live it is notably more expensive than very solid Samsung tablets (and Samsung has a strong retail/support infrastructure in my country).
The price is a deal breaker for me, although I am glad such a device exists.