Thought I'd write a review for this since there are none: The premise is pretty straightforward - MC dies and gets reincarnated in another world.
As the title and the synopsis of the series implies, he gets a special ability that allows him to gain XP at a much higher rate. There are of course other aspects to his abilities which could be said are even more interesting that just the high XP gain, and these are revealed as the plot moves forward.
There is very little art, just the cover pages, so mostly one has to imagine the various looks of new characters that might
not have gotten any space on the cover.
The story is narrated from the MC's POV, while it also includes side stories in between that are relevant to the plot; these are narrated from a 3rd person POV. The author felt like a troll for some time - the main story, narrated by the MC, is mostly slow-moving SoL, while the side stories, though just a few, contain the actual mysteries and excitement relevant to the plot, and these don't come up often enough initially.
This gets tedious at times though, because the side stories can regularly make the main story seem irrelevant and silly, even boring, yet the series is mostly about this main story. But the stories merge after a while, and things have gone back to SoL for now
Since it's the MC's POV, the focus is mostly on him. His monologues can get a bit tedious to read at times, but are funny at some other times. He isn't the smartest but also not the dumbest of MCs.
Character development is very minor, MC changes his view on certain things early on, and the side characters (basically, his harem + some friends he makes) get focus from MC's POV majority of the time, like when he converses with them or when the MC observes their expressions and reactions.
(MC also has a younger sister in his original world (earth), how she plays a part in this story is also enjoyable)
The relationship development is very quick, there isn't a lot of romance but MC and his main girl engage in other acts early on, which I have hardly seen in many harem novels. As typical of a harem, the girls fall for him quickly, and fortunately there aren't any annoying tsundere characters so far. There're no "beat him up because he saw us naked by accident" incidents either, which is a big relief. MC also seems open to multiple love interests.
No strong cliche character tropes (yet), and almost all conflicts with enemies get resolved very quickly thanks to MC's unique abilities.
Overall a light and decent read if you are reading/watching other things, there's hardly any excessive drama/tension which keeps things simple, but it's not something I could binge-read. Fan translation is fairly quick and of good quality as well