Both the original Amazon Kindle Fire HD and the Kindle Fire HD 8.9 are grown up e-readers that are also great for watching films, browsing the web, emailing and playing games. You can install apps, listen to music, and - yes - read books.
With their heavily customised Android operating system the Kindle Fire HDs are well-priced full-blown tablets, even if they are tied in to Amazon's world.
You can buy books, music, games, apps and movies - but you have to buy them from Amazon. That's not a problem as Amazon's pretty well stocked on that score. But it does illustrate the limitations of the Kindle Fire. You can install third-party apps, but it requires some technical knowledge.
In Amazon's own app store you'll find Netflix and BBC iPlayer, but ITV Player and 4oD remain conspicuous by their absence.
As you might expect, finding and reading books using a Kindle Fire HD is a great experience, even allowing for the extra weight.
The Kindle Fire HD 8.9 looks very similar to the 7-inch Kindle Fire HD - it's simply stretched to incorporate a bigger screen. Both are designed to be used in landscape format for everything but reading books.
Build quality is the same too: they're robust and built to last but lack a little of the stylish finish of iPads or google Nexus tablets.
The two tablets have ports, features and buttons in similar places. On the bottom edge are micro-USB and micro-HDMI ports, and the headphone jack sits near the top. Speakers are seated to the left and the right on the rear, and the webcam is in the middle above the screen.
Volume and power buttons are on the right-hand side, flush with the body. This can make them hard to find by touch alone. They also both suffer from a niggle with the keyboard in which the back button in the status bar sometimes sits to the right and you instinctively tap it to delete, instead of using the Delete key on the keyboard itself.
When it comes to the screen, arguably the most important part of a tablet, both Kindle Fire HDs have IPS panels. Viewing angles are wide, colours are deep and contrast is good on both. Here, the 8.9in device makes up for its heavier weight with a bigger, more detailed screen, though.
Being blunt, the 7-inch Kindle Fire HD wasn't as fast as we'd have liked. In use it doesn't feel as snappy as an iPad mini or Nexus 7, especially when browsing the web or launching apps.
The Kindle Fire HD 8.9 has a faster processor but this doesn't make it feel noticeably zippier in general use. However, the Fire HD 8.9 pretty much matches the Nexus 7 in our benchmarks.
Both Kindles offer good battery life. However, neither includes a mains charger in the box, and the Fire HD 8.9in will take 14 hours to charge from you’re a computer's USB port.
You can choose either 16 or 32GB of storage for each Fire HD and neither allows you to add more storage. Bear in mind that not all of that is available to store apps and media - it's around 4GB less.
There's little to choose between these two devices in terms of build, design and performance. If you already own a Kindle or have bought ebooks using the Kindle app on another platform, making the switch to the 7- or 8.9in Kindle Fire HD will be very easy.
Which should you choose, though? There are three key factors: price, screen size and weight.
If you pay extra for the 8.9in version you get a bigger screen that has better resolution - so if watching HD movies is your thing it may be worth the outlay. But if you're a bookworm, the 7in device will offer a better, lighter reading experience. And save you some pennies.