I've been through the same thing with my e-reader dying on me after a clumsy moment and and finding one that shines in bright light changed my outdoor reading game. You want something with an e-ink display that cuts down on glare and making pages look like real paper even under the sun. Battery life is crucial for those park sessions or trips, so aim for models that go weeks without needing a plug.
Portability means lightweight and slim, easy to slip into a backpack. And for your eyes, adjustable fonts are a must-have, letting you tweak sizes without strain. Check out options on that model that fit under $150, plenty out there with these features. Works great.