Almost as soon as Microsoft announced the Surface RT and Surface Pro in 2012, there was an immediate reaction: "OK, that's sort of nice, I guess, but when will there be a Surface laptop?"

There's never been any doubt about the Surface line's build quality, attention to detail, and aesthetics. But for many of us, a tablet with a kickstand and separate keyboard lacks an essential quality: lapability. The Surface Pro 3's variable-position kickstand and more secure magnetic keyboard attachment meant that the thing could be used on your lap at a pinch, but it never had the stability or convenience of a true laptop with a stiff hinge, and no matter how much Microsoft claimed it to be a laptop replacement, it wasn't.

The Surface Book is a laptop replacement.

It adds the thing that the Surface Pro lacks: a stiff hinge. It's still a tablet with a separate keyboard, but this time around, there's no kickstand. The hinge holds the screen up and lets you hold the screen at whatever angle you want. This fixes the lapability problem once and for all: the first thing I did when I got my hands on it was sit down and put it on my lap, the way I do when I'm on a plane or watching TV. And it worked. I could set the keyboard just so, the footprint of the device on my lap wasn't deceptively oversized (extended by the kickstand), and the screen was at just the right angle. The greatest problem of the Surface Pro 4 is addressed by the Surface Book.

The "dynamic fulcrum hinge," as Microsoft calls it, is an unusual design. With the system closed, it's semicircular, but open it up and it unrolls, slightly enlarging the footprint of the machine. This helps keep the system balanced when it's on your lap.

But Microsoft is still committed to the 2-in-1 concept, and the Surface Book doesn't buck that trend. The screen is firmly anchored into the keyboard/battery base, but press the eject button (or use the software eject button from the Windows notification area) and it comes loose. The result is an astonishingly thin, albeit rather large—it has a 13.5-inch, 3000×2000 screen—standalone tablet. Hold it like a clipboard, draw on it with a pen, poke at it with your finger.

The screen, at least in the less-than-brightly lit moody atmosphere of Microsoft's hands-on session, looked bright and beautiful. 3000×2000 is an unusual resolution—it looks like Microsoft has decided to ditch the variety of weird and wonderful resolutions that are found in the PC world, typically derived from strange multiples of VGA's 640×480 resolution—but it means that there are a ton of pixels on the screen: 6 million of them, 267 per inch. Viewing angles were good, and both touch and pen responsiveness were solid.

And the keyboard unit itself? Both the keys and the touchpad eclipse anything previously branded Surface. Type Covers aren't bad, and the newest one designed for Surface Pro 4 is the best yet, but they still compromise a certain amount of feel in the name of being thin. The Book's keyboard doesn't, and the keys feel crisp with good travel.

Aside from lapability, the weakest part of the previous Surfaces has been their touchpads; undersized and imprecise. The glass touchpad on the Surface Book feels vastly better. It's going to take extended testing to get a real sense of how it compares to Apple's touchpads, but at the very least this one should be usable without leaving users aching for a mouse.

The look of the thing is going to be divisive. That dynamic fulcrum hinge doesn't completely close; the screen isn't flush against the keyboard. Look from the side and there's a gap.

The gap is going to drive some people crazy. I don't mind it at all. Much like many of Apple's machines (and, like it or not, they're still the benchmark against which all others are judged, as Apple has consistently managed to build high quality laptops for many years), it feels solid, well-engineered, and designed. Like other Surfaces, the magnesium alloy Surface Book has a plain, unadorned, almost industrial look to it. It won't be to everyone's taste.

The Surface Book should offer another feature found in laptops: better performance. The keyboard unit can include a discrete NVIDIA GPU. That's only usable when the tablet is docked, of course. The keyboard also includes an extra battery; the system as a whole can manage a 12 hour battery life, Microsoft says, but that's only when using both batteries. The tablet itself has much less battery life.

The one sour point is the price. The Surface Book starts at $1,499 for a Core i5, 8GB RAM, and a 128GB PCIe SSD. But there's a catch: that system doesn't include a discrete GPU. The cheapest Surface Book with the discrete GPU is $1,899. That's still a Core i5 with 8GB, though it also ups the storage to 256GB. The top spec is a Core i7 with 16GB RAM and a 512GB SSD, and that costs an eye-watering $2,699.

We'll have a full review of the Surface Book in due course. But from what we've seen and used so far, this time around, Microsoft really does have its laptop replacement.

Listing image by Andrew Cunningham