It's rare that a product could be called revolutionary in its thinking, but that's certainly an accolade that could be awarded to the Lenovo Yoga Book. For this 10.1-inch convertible is about as far removed from a laptop as we've seen, while still, essentially, being one.

To explain: the Lenovo Yoga Book has a keyboard without physical keys, called a Halo Keyboard. It learns your hand positioning over time to compensate for typing mistakes. It even offers predictive word completion, much like a phone's predictive text.

It also comes with a physical stylus that can be used for handwriting or drawing directly onto the would-be keyboard panel - or, using the pen nib, you can write on real paper with a pad positioned above and this input is mirrored in digital form. That's thanks to the EMR writing surface, which has 2,048 levels of pressure that you can almost "feel" when writing, drawing or, as we did, scribbling various things down.

So the Lenovo Yoga Book is like Wacom tablet meets laptop, meets tablet, meets the future. The Yoga Book is, indeed, without compare.

It's also initially tricky to use. On first go its typing experience, with its limited haptic feedback, felt off. And second. But having used the device for a good 30-minutes following our first try, this keyless keyboard, against the odds, really does begin to click. It's such a compelling concept - and one we think tech adopters will be keen to try.

Sure, your word rate is going to be lower on this if you're writing a novel, but for notes, sharing and even digital backup it makes a lot of sense for productivity's sake. It's a marriage of ideas that is that rare thing in tech: original.

However, given the size the trackpad, which is marked out with left and right portions in the Windows device, and five dots in the Android device, we continued to find navigation around the screen a little tricky. It's sensitivity adjustable within the software, though, which fixed our experience. Plus, as the device has a touchscreen, the combination of touch, type and pen makes for a complete experience.

Then there's the Real Pen accessory, which is a bit like it sounds: it can accept real ball-point pen nibs, or these can be popped out and replaced with the stylus-like nib. Why would you want a real pen for a laptop, you probably wonder? Because the Yoga Book can detect real handwriting on paper placed above its surface and transform this into on-screen notes. Or ditch the paper and, with the press of a button the keyboard layout vanishes, ready for you to scrawl away with the stylus tip for input. It's an unprecedented concept that will suit different users in different ways.

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It's also the world's thinnest convertible, at just 9.6mm thick when shut closed. And its 690g weight makes it not much heavier than most tablets. That a product three years in the works can be created so thin is a testament to Lenovo's design team - just look at those slender edges (the screen side is a mere 4mm).

However, the Yoga Book does lack some of the mod cons: there's no USB Type-C for example, instead it's built on microUSB 3.0. Which is fine, but seems a little out of date. The Intel Atom x64 processor on board isn't the most spritely either, especially for a Windows setup, but that's the payoff for a device so small and light. Still, with that lightweight hardware, the 8500mAh battery is said to last for as long as 15-hours per charge.

Operating system is a user choice: the Yoga Book comes in Android (£449) or Windows (£549) forms. Android is version 6.0, with moderate tweaks - a "task bar" with current open apps and multi-app window support, a little like that in some larger Samsung phones - to make for better multi-tasking.

Given that many Yoga products with the high-grade 3-axis hinge come in at a much higher price points, it makes the Yoga Book a truly compelling proposition and a genuinely original product.

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The Yoga Book is one of the most exciting tech products we've seen in some time; it's the laptop reinvented. But the learning curve for some - those of us stuck in our old ways - might make it too tricky to use. Not the product for everyone, then, but certainly an innovation.