The two devices driving this show are "lost in another world" and "time loops/reset points", and as such the basic formula proceeds with each episode containing some trial-and-error as protagonist Subaru dies gruesomely to various foes and hazards he could not have anticipated, and after multiple attempts he eventually finds a route to navigate all of them safely and accomplish his goals.
Subaru is the main character, but is also more of a plot device than a well-characterized figure. His actions and awareness are all over the place; sometimes he looks like a genius, other times a hopeless harem-style protagonist. In the last third of the show a major development moment is shown that changes his basic outlook into a more confident, collected and determined main character, but it also has the effect of making him more one-dimensional, which is a complaint common to most of the characters in this story:
The plotting is driven around creating escalating cliffhanger situations out of thin air, and the characters decide to do things because the plot demands it, rather than because it has been artfully set up. By the conclusion, one gets a sense of progression, but the progression is grounded in abstract themes, not the characters, and since the plot has not really concluded(there's lots more material to adapt) it's not a totally satisfying ending either. The characters are good enough to keep you invested, but not much more, and because the plot jerks them around and occasionally kills them, there isn't smooth consistent gratification in these characters, indeed the author has actively campaigned against your building that kind of relationship to them, so if you just want comfort zone waifus and husbandos, stay away. (90% of the negative reaction to this show is people realizing at some point that they have been deceived and will never get what they want.)
Despite those concerns, the basic formula works. There's plenty of material to keep you guessing. White Fox has done some great work on the adaptation and several of these episodes are downright breathtaking to watch. But go into it looking for a bit more of a literary experience, where the concept and themes dominate the proceedings, even as it makes occasional, surface-level pandering motions.
