OK, I bought it. But, riddle me this, riddle me that - is it powered by the "dumb PoE" (12V - 24V), or the cool way - 802.3af/at?! Look at the product page - in the summary at the top, it says it supports up to 57V (it's why I bought it!!!), but when it arrived and I opened the box, it said it only takes up to 24V. Damn! Looked at the product description on the website - 12V-24V it says. But, in the summary at the top, it still insists that the device runs on up to 57V. So, make up your mind, which one is true?! Am I going to damage it if I run it at 57V? If so, I don't want it, I want to return it.
You should open a ticket with support.
Even on the manual:
It says:
Power PoE-IN (802.3af/at), 12-28 V
which makes no sense, as to be 802.3af/at compliant It should support 37-57V per standard.
And below:
The device accepts 12-28V DC via PoE 802.3af/at.
A power supply and PoE injector are included [1]
It could well be a mistake, but surely It Is a serious one.
I doubt that they could declare compatibility to a standard (802.3af/at) by mistake, so It Is more likely that the 12-28 V Is the mistake, but ask support.
In theory a non 802.3af/at device will be detected by the power supply (PSE) that won't power it, so the risks of frying it with a standard PSE are very low, but better be safe than sorry.
[1] definitely these are "passive" and are not 802.3af/at compliant
I opened a ticket. Let's see what they will say. Meanwhile, the device remains powered through an Ubiquiti Instant AF power converter. I know MikroTik has a device that does that, too, I have it also, but it's so chunky and inconvenient ...
Let us know how it goes. 
They did not lie about the included power adapter and PoE injector, that's for sure. They do supply the already well-known gigabit passive PoE injector - the short white cable, that has a RJ-45 insert on one end (for a cable to run DATA+POWER towards the device) and a RJ-45 connector + 5.5/2.5mm barrel jack for a power adapter on the other - and a tiny power adapter, like the one you would get with the original hEX router, back in the day. And, yes, it's a 24V adapter.
In their defense, though, the device seems to work pretty well with that cheap Quectel LTE4 modem. I have it deployed at a remote location (in a village), with the cell tower I have it aimed at being a little over 7km away in a straight line. The little devil gives me about 80-90Mbps down at the beginning, then quickly drops to a stable 50-60Mbps down with 35-40Mbps up (depending on the celltower load at the moment) in the B3 band. Those are some decent damn speeds for LTE in the fields. I also use it as the router on site, running a WireGuard S2S tunnel to another MikroTik router, and have it monitored via SNMP in Observium through the tunnel: 51-54 degrees Celsius on the CPU, while the heat here is about 30 at noon, is not a result to be shy about! The only thing I found weird in my hands is the plastic housing that seems to flex a little more than I expected - don't know if it would survive a hail in the summer, or the ice chunks falling from the sky will shatter it to pieces. But then, at that ridiculous price, would you really care if it survives?
Really, the only thing it's missing, is pure 802.3af/at support, in my opinion. Please, MikroTik, fix that! Other than that, thumbs up!
Alright, they replied. Apology accepted. They admitted a human error was made, while making the documentation. It has been fixed now. I mean, the product description has been revised, not that they suddenly added 802.3af/at capability to the device. 
It is, indeed, only powered by 12V-28V power sources. If you want to run it on true PoE (a switch or an injector), a 57V-24V stepdown converter of some kind is needed. Shame, but it is what it is. So far, it has been running smoothly, no complaints, except maybe that the signal reception isn't quite stable and fluctuates anywhere between -73 dBm and -65 dBm every few seconds. Not sure if it is some resonance due to antenna design, or it has to do with the cell tower and signal reflection off moving objects (cars, busses, trucks along the main road). Or if it's just RouterOS displaying bullsh*t.
Frankly, I hope they consider the possibility of a "Plus" model that adds carrier aggregation (the current model is single-band only), 802.3af/at power (this time, for real!), maybe a bit higher antenna gain. That would be fantastic.