If the above options aren't doing it for you, the below picks are better. If you can find them for dirt cheap, it's worth looking at old Nooks, Nooks with books, and the like. The older they get, the slower they are, with less efficient batteries and laggy screens. If you can test it out in person before buying, that's great.
The basic kindle costs $110 without ads and is a few years old It's not waterproof, but it has a front light that makes it readable in a dark room, and it can be used to listen to audiobooks.
The included stylus allows you to mark up books or create notebooks on the e-reader. It's perfect for class. The big screen is nice, but it costs a lot.
The Barnes & Noble Glowlight 4 has more storage than the Glowlight 4E, and it has a night mode for more comfort.