Well, this truly is the "little brother" to the "Portal" series, as it takes place in the same in-universe and uses a lot of similar game mechanics, but it also mixes things up with elements from "The Talos Principle" etc, mainly the light beam puzzles that seem to be lifted straight from that game. In no means is that a bad thing, though, since the gameplay is fairly challenging at times and quite simple at others, depending on how good you are with puzzle games in general (and how much you enjoy them).
The narrative story of "Lightmatter" does require you to listen a lot, but it does not make you stop while listening, unlike a bunch of other games do (you can rush towards the exit and not be afraid the dialog will be cut short at any moment). If you are willing, you will notice (and possibly enjoy) the little references and breadcrumbs here and there that may seem familiar, if you have had prior dealings with Aperture Science.
Overall, it is a fractured 8.5/10 from me, since the experience is quite short-lived, if you are really good at puzzle solving and blaze through the game on your first try. In my case, there were a few situations where I was quite lost for a while until it "AhaAAAah!!"-d on me and I am very OK with that. Next, please!

Frustrating puzzles, not because they're hard, but because each time you make any kind of mistake it is met with immediate death. Bad level design, unclear where the exit is half the time. Constant crashes and frame drops. The game is super short, which would be fine if it wasn't repetitive.

It wants to be portal so bad but its concept is not translated very well into gameplay.

Also blatantly referencing portal in your mediocre game is embarrassing!!!

This game might initially seem just like a portal clone but it is definitely it's own thing. Yes it has a voice of someone talking (and insulting) you throughout the game who is the villain. Yes you, as the silent protagonist, go into rooms and solve puzzles to get to the next room. Yes it is funny when it wants to be. However despite that it really comes across as having it's own unique style. Its much darker in tone than portal and has its moments (especially towards the end) where the humour complete fades to be replaced with a sense that something truly horrible is going on.The antagonist is great. He is the right amount of up his own derriere, smart and ruthless to come across as an interesting bad guy for you to rebel against. The puzzles involve directing multiple lights to open doors and are equally frustrating and fun.The only thing which sometimes felt like a tacked on thing is the small amount of platforming but it isn't bad just not as good as the other bits.Overall if you like portal you'll probably like this. Not because it is the same but because you clearly have good taste.