I read the first volume of this some time back, and enjoyed it sufficiently that I was quite looking forward to the series. It's not an unreasonable effort.
"Rimuru" is a Japanese salaryman, who has an unfortunate run in with a random stabber when out one day to meet his mentee and their new partner. Since he's a terribly reponsible chap, he doesn't think twice about leaping in front of the knife to protect his junior and his paramour, and this leads to him bleeding out rather horribly in the street.
It's at this point that some vague unknowable great power steps in, to grant him a new life in another world. (I won't say "oh no, not another ruddy isekai" if you don't.) But as he's dying, he runs through the usual thoughts: "I wish this hurt less"; "Why do I feel so cold?" and "Oh god, I hope no one finds my folder of porn."
Which means that the strange power that's driving his reincarnation has a few different stimuli that it can use to determine his new life. Previously, these have been such things as "being a spider" or "really liking snacks", but here, it's basically not liking any sort of pain and being able to survive anything. So when he comes back to life, he's a slime.
Slimes are mostly immune to hot and cold, are quite hard to stab, and he's got the very nifty talent of being able to steal the powers and forms of whatever he can absorb. This turns out to be more or less anything. Yes, unfortunately, he turns overpowered within the first episode. If you're hoping for some actual threat here, you're going to be disappointed.
Adding to that gamebreaker nature is the fact that he has in his head some form of living wikipedia, which can tell him about anything he might discover, and what he can do with the resources at his disposal. This is at least an interesting trick however, and does happen to have some impressively psychedelic visual effects, that are actually pretty damn cool. Just about justifies having a Deus Ex Machina at his beck and call.
He then goes on crazy adventures, which thus far have involved protecting some goblins, punching a whole bunch of wolves and shrinking and then absorbing a dragon. It's for plot reasons, I'm sure it'll be important later. And then the plot finally gets serious with a confrontation with various political leaders. In the form of a bar fight. All of this leads to it turning into a civilisation builder, as might be seen in similar LitRPG type plots.
Still, it's doing well in the "not taking itself seriously" front, such that it's enjoyable to watch. It'll be interesting to see if it can maintain that edge, especially when, as far as I can tell from the opening, the slime gains the ability to turn into a tiny girl. A lot of the humour comes from emotions and visual reactions coming out a slime, and if he goes human most of the time, that'll get lost.
It's a little more engaging than a lot of the isekai have been recently, enough that I'll keep it on my watch list, but I suspect it will struggle to reach any degree of exceptionalism.