UPDATE:
Changed rating from 3 stars to 5 stars, mostly because the seller has been extremely responsive and helpful. After more experimentation the eggs I cook are coming out more consistent now.
Kudos to Cheman's service staff for their excellent and quick responses.

Original review:
With some experimentation, this device will cook eggs, but note that results are inconsistent. For example, cooking smaller eggs requires less time than cooking larger eggs. Note that the "jumbo" eggs sold by my local grocers do not fit in this egg cooker. "Large" eggs fit, barely, though the shells make contact with the plastic lid.
Upon initial use, the cooker leaked much water. However, I discovered that securing the lid such that the steam vent is on the side opposite the power switch, then no leaking is observed. Apparently the lid does fit quite the same in each position [on the unit I received]. For me, this is a non-issue because the "fix" is so easy.
The cook time seems to vary quite a bit. I experimented with 4 sets of 6 eggs, all picked for approximate uniform size. Results for the4 sets of 6 eggs (with lid secured to prevent leakage): the timer signal began at start + 10:19, 15:02, 11:45 and 10:53. The eggs that cooked for 15:02 were "hard boiled", but the others were not. More time is required; perhaps adding slightly more water would remedy the premature auto-shutoff (which shuts off the heat, but not the audio alarm).
Minor point: The user manual uses the word "tray" in some places, and in other places it uses the word "rack"; meaning the same thing. The diagram fails to show the tray/rack post, nor is the post mentioned anywhere. Not a problem, but it comes across as unprofessional.
Be advised: Use a mitt or something to protect your hand when moving the egg tray/rack from the cooker into cold water, because it is extremely hot.
The manual refers to the audio alarm as a "buzzer", but it is a high-pitch electronic alarm, and is barely audible even at close range to those who suffer from mild or worse high-frequency hearing loss. Of the elderly folks in the room at the times it was sounding, not any of them could hear it, unless they put their head right beside the cooker.
BOTTOM LINE: Carefully match egg size for better results, and BE THERE at expected finish time because it tends to shut off prematurely.

Makes consistent freshly-boiled eggs with no hassle, timing, or watching the pot.

Choose your own level of done-ness by measuring out more or less water in the provided cup, and the eggs cook exactly the same each time. Everything you need is in the kit including a recessed pin for poking a vent hole in eggs before cooking.

Use distilled or filtered water and rinse the eggs before cooking, to keep the heating element clear of sediment and reduce your clean-up work.

We use this a few times a week so that we have fresh boiled eggs on hand for recipes and snacks.

This egg cooker is fantastic. As soon as it arrived (on time) I made two poached eggs, perfect. There was no info in the pamphlet that came with it as to if you should use room temp eggs so I put two eggs in straight from the fridge, and made two soft boiled eggs(the next day). They also came out perfect. This tells me two things...the water measuring cup is right on the mark,and it must be designed for cold eggs. The hard boiled eggs I made two days later were not over cooked and were easy to peel. The bonus about this egg cooker is the size, very compact and easily stored. One feature that stood out from the other cookers is the post that goes in the middle of the egg tray makes it very easy to remove the cooked eggs from the cooker. The post is where the seventh egg goes in other cookers. If you are thinking of getting an egg cooker this is the one you want

I've generally avoided single use kitchen appliances as counter-cluttering and not worth the money. However, this egg cooker is totally different! Making perfect eggs is super simple! This little unit takes up very little space but gives you the option of making perfectly cooked hard boiled and poached eggs. All you do is pour water into the heating tray and then place eggs on top of the egg holder. Put the lid on, press the button and wait for the timer to go off. Voila! Beautifully cooked eggs. Poaching eggs is no more difficult. Poached eggs on top of avocado toast is now my go-to breakfast. I don't have to mess with a pot or little eggs strands all over the place from poaching directly in water. Cleaning the egg cooker is much easier. It makes six hard boiled eggs or two poached eggs.

We used to boil eggs the traditional way by boiling them in water, but doing that everyday was such a hassle, we saw this on Amazon and immediately jumped on it because my wife wanted something easy to boil everyday and the ability to get her eggs soft or hard.

The Chefman egg cooker delivers everything she wanted including ability to get the eggs cooked a little soft inside or a bit harder by tweaking the settings. The device itself is pretty easy to use and wastes less water than boiling the eggs in water, it also works as advertised based on the instructions in the book supplied.

The one thing we like about this is that it also comes with some extra trays to cook eggs within the device, we use it to cook eggs over easy and it's pretty good.

While I did give this 5-star, my one small gripe is that it does not come with an internal timer which would have been great, hope they incorporate that in a newer product and I would buy that as well.