You can get the Kindle app and sideload it onto a Vox. Available
here and other places as well. I can't tell you how well it works, having never tried it.
What do you want to do with the tablet besides reading?
While my family has two, they are used exclusively by my kids as the Kobos cannot handle what I need them for. The Vox is great for reading, videos, simple games, making notes and I would recommend it for such. The screen is great, more usable in sunlight than most other screens.
If you need GPS, camera, microphone, Blue tooth, etc, you'll be disapointed in the Vox. I use an Acer A100 and it's a good deal if you can find it cheap (screen and battery life are not as good as other tablets out there, but not deal breakers for me).