I have the original Kindle HD Fire and for less than £130 at the time, it doubles as a tablet and much cheaper! The original Kindle HD's let you download your own browser so I didn't have to use Silk, but Silk has improved, so am not worried if I need to upgrade. I'll know when the battery holds the charge for less time/use.
Am studying for a course, so I can highlight in books I need to read to create notes, or search out information. Much more efficient than a traditional book.
Illustrations, charts, etc even though in colour, don't always do well, so I find myself having to get the book now and then. I can also transfer pdfs to it from my desktop as that is the format of most academic papers.
Living in a flat, I'd be over-run with books, so Kindle has saved me a lot of space. I do still like to read a real book now and then, and all past editions are not always re-published as e-books.