For the first three generations, "Microsoft Surface" meant a Windows-running tablet with a snap-on keyboard that turns it into a laptop. But today that Surface definition has expanded, now including a new device where the tablet part takes a backseat. Though it costs a pretty penny, the Surface Book is one badass laptop.

Unlike the Surface Book, Microsoft's Surface Pro series walks a tightrope, trying to balance the strengths of tablets and laptops at the same time. Though Microsoft has done a great job minimizing the compromise in that approach, some tradeoffs are inevitable.

But the Surface Book? First and foremost, this is a great Windows 10 laptop. It's the first Surface that feels 100 percent uncompromised as a notebook.

It does requires one big compromise – you can only use it as a tablet in short bursts – but the Surface Book also makes for a surprisingly good tablet, thanks to Microsoft's battery setup.

The main (bigger) battery lives inside of the device's keyboard, so when you're in laptop mode you get the long battery life you'd expect from a modern high-end notebook. But there's also a second (smaller) battery hiding inside the screen. With the press of a button, you can detach the screen for what Microsoft calls Clipboard Mode.

In case you're confused, "Clipboard Mode" is the same as "tablet mode." We're guessing Microsoft changed the term here to lower expectations. Tablet batteries are supposed to last all day long, so the company needed a new word for a huge tablet you can only use in short bursts. "Clipboard" works as well as anything.

The Surface Book's 13.5-inch display is a great all-purpose size for a laptop, but it also works well for an oversized slate. It has sharp 267 PPI resolution, and (unlike past Surfaces) doesn't lose its crispness when you move in closer for tablet mode.

That smaller battery in the screen means short battery life, but it makes the Surface Book's clipboard feel incredibly light in hand. It's much larger than the Surface Pro 4, but (sans keyboard) weighs either 6 percent lighter (compared to Core m3 Surface Pro 4) or 9 percent lighter (compared to all other SP4 models).

Bigger size and lighter weight – combined with its premium magnesium build – means it feels terrific in hand.

That short tablet battery life is going to be a bigger deal for some people than others. If you use 2-in-1s in tablet mode as much as you do laptop mode, then the Surface Book isn't for you. In clipboard mode, crank its brightness up high, and you can expect no more than 90 minutes to two hours between charges (if that).

In laptop mode, it's outstanding. The keyboard and large glass trackpad are every bit as good as what you'll find on a MacBook, and it has the bonuses of touchscreen and pen input that you won't find on any Apple-made laptop.

There's also a third mode where you can remove the Surface Book's screen and reattach it backwards. The most obvious use for this is propping the screen up to watch videos, but you can also angle it more horizontally, for artistic uses like Photoshop and Lightroom. Here the device essentially become a canvas:

Performance will vary from model to model, but in our entry-level review unit (Core i5, 8 GB RAM) we have few complaints. Early in our testing we had an issue where the fan was running non-stop, but after performing a Windows 10 refresh we managed to pin that on a misbehaving third-party app (Mailbird). After uninstalling it, there haven't been any heating issues or hurricane-strength fans.

Our Geekbench 3 runthrough has the Surface Book scoring 3,105 in single core and 6,561 in multi core – even this entry-level model is a very powerful machine. You can read the full stats of our benchmark here.

There is one persistent bug, where we intermittently get a notification saying the display driver has stopped responding. It recovers immediately every time and has yet to stop our workflow, but Microsoft would be wise to squash this bug as soon as possible.

Microsoft included a special camera in the new Surfaces that lets you log into Windows using secure facial recognition technology. This is at least as big of a deal on devices like this as fingerprint sensors have been on phones: it takes just a few seconds to set up, and after that you can securely log into your Surface just by looking at it. It takes only a second or two, has worked perfectly for us and saves you from typing your PIN or password every time you sit down.

In laptop mode, battery life is great. In our video streaming test (over Wi-Fi, with brightness at 75 percent and no major background apps running) the Surface Book only dropped 9 percent per hour – that's better than most smartphones we test. When we ran the same test on the Surface Pro 3 (right after it released in mid 2014) it dropped over 15 percent per hour.

Our only hesitation in recommending the Surface Book is its pricing: starting at US$1,499 for a 128 GB SSD, it's expensive enough to make Apple's MacBook pricing look tame by comparison. It would have been nice to see the Surface Book starting in the $1,350 range, to make it a true rival to the MacBook Pro. But, on the other hand, if that would have meant compromising any of the fine details in this beast, then we can live with that.

As it stands now, Microsoft's two 2015 flagships present you with a tough decision. You can either get the smaller Surface Pro 4, which has much better tablet battery life but is also a smaller device, or you can throw down an extra $400-500 for the Surface Book, which makes for a bigger and better laptop.

We have both new Surfaces in house and will run a full comparison post before long (and stay tuned for our full Surface Pro 4 review as well).

We think Microsoft knocked it out of the park with the Surface Book. It isn't for everyone, but if laptop with short bursts of tablet awesomeness sounds like something that can fit into your workflow, we think you'll be very happy.

The Surface Book is available now (though back-ordered everywhere), starting at $1,499 for this Core i5, 8 GB RAM, 128 GB SSD model.

Product page: Microsoft

This review was updated on 11/4 to mention that the display driver bug hasn't yet been fixed.

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