You might consider the Jetbook. It is LCD rather than eInk and supports .txt books very well. It supports custom folders in the eBook menu. The page turns very fast with no flash at all... the text is sharp and easy to read in well light room. It can also be read in sunlight but can glare a bit.
This is a 5inch screen device, and very sturdy and won't be susceptible to easily broken eInk screen as you can see many people have had to contend with by reading other threads. (Perhaps might be an issue with an 11yo.)
See my review and $50 coupon.
https://www.mobileread.com/forums/showthread.php?t=23953
BOb