BAD! That one word sums up this laughable excuse for a novel. The MC is a weak gun obsessed looser. the setting is boring, the flow of the story is language and sub par, the side characters are even weaker and the female romance lead was a 10 year old girl by the time I dropped this series. If I were to die at the age of 30, reincarnate with full memories, would I fall in love with a 10 year old as a 40 year old? Nah, just pure BS. Unless you actually are reborn without any memories, you don't do that, well, unless you are a lonely pedophile from the start. The only ones that could even like this pile of dung, are people in the same position as the male lead. Seeing all these "reincarnation" into other worlds as a super powerful hero novels that have skyrocketed in popularity, makes me loose faith in humanity. While a there are a few pretty good and highly entertaining novels in this genre out there, this one is not. Shifting through all these crap novels to find a few grains of gold is hard work, so my advise is just don't bother with this one and move one to something better. Try something like Douluo Dalu if you want a good reincarnation story. It is everything this one is not, in a good way.
The main problem with the Japanese form of this genre, are the atrocious male leads. They are just worthless, spineless, uninspiring losers who gets a new chance, this time with OP superpowers, and a harem of girls for no apparent reason. Then again, the weak, looser archetype male leads in anime, mangas and LN's, has been longstanding problem and is slowly killing the industry imo.
Ok, that might be a bit harsh, I understand the appeal of novels like this. I too liked fantasy novels in this vein, when I was around 13 and didn't know any better. I highly doubt the western readers of this series are in their early teens though.