A Kindle reader is certainly not an all-solution reading device at least in its current avatar. I don’t mean to say that there should be social features or there should be multimedia or other such fancy features. But if you want to recommend a device for students as well as people for all ages, a tablet is far better than a Kindle reader.
First of all, images and graphics don’t look good in a Kindle reader. They are black-and-white first of all. And even the rendering is not as good as it is on tablet screens, especially higher end Android devices as well as the iPads.
Another problem is that if you want to make lots of notes the keyboard is not as good as the one you get with a tablet especially when these days you easily get virtual keyboards with swiping facilities (you simply drag your fingers on the keyboard instead of tapping individual alphabets or numerals). People may not realise it right now, the ability to swipe instead of tap is a very big deal especially when you do lots of typing on the screen.
Am I advising you not to use the Kindle reader or another such device? Not at all. It is definitely a great reading experience because one, you almost feel like reading off a paper and two, there are practically no distractions. The device is just for reading and nothing else and this is a big plus. For just reading text my choice will always be an e-ink reader. But if there are lots of images (for instance, a book for my daughter) or if I need to make lots of notes (for instance, one needs to make notes to review the book later), the tablet would be my first choice.