I often enjoy stories where the MC lacks normal human emotion as such things can be used to move the story along. Here however MCs lack of emotion because she is a vampire is used to make the story bland. Admittedly this was not the case until the second half of the book, hence the two stars. The story also lacks resolution.
The story (don't read if you are concerned about spoilers). MC is a young vampire girl. Her mother is a concubine to the vampire lord but concubines are not favored. This results in MC living in poor but paid for housing receiving poor but paid for food. In this world vampires are strong and fast and have high powered regeneration but can otherwise be killed just like anyone else. Therefore the vampire lord will eventually die and when that happens MC and her mother will be out on the street. To prepare for this MC, who remembers her prior life in Japan, begins training at a very young age. This results in MC joining the adventurers guild at 10 and likely being the most powerful adventurer in that branch of the guild.
The MC's power is largely ignored or overlooked as she adventures alone in the dungeon. On one such occasion MC encounters a rich trader who is the sole survivor of dungeon dive the trader financed to find good for his trading house. The MC saves the trader and sells him the recipe for chocolate which brings her a lot of money.
Later the MC is required to attend the house heir’s coming of age party where she avoids the lime light until a disgruntled relative releases a very powerful monster. Forced by circumstances to kill the monster the vampire lord (MC’s father) negotiates MC into becoming the new heir.
MC goes clothes shopping for her new role as heir with a half-sister. Half-sister is kidnapped but MC catches the kidnappers and the person behind the crime in a very public way. This results in MC getting a bunch of marriage proposals. The end except for the regret I feel at having wasted money and time.
The plot's a bit too aimless and the characters are one-dimensional. I don't recommend this book.
But, if you're just looking for a simple story of a reincarnation making up for their (vague) regrets of dying pointlessly, you might be satisfied with this book. The titular Mercedes trains and studies daily, but it's glossed over so that you don't have to feel any of the effort that she put in. Just rote memorisation and training with ever increasing weights. You won't feel a thing as she becomes the second most powerful thing in the story. All this, fueled by regret and a will to survive.
There's also some mystery about the nature of the world and the mechanics of magic, but it just feels like superfluous wrinkles in an otherwise generic fantasy set in an era of medieval-ish technology and culture. Dungeons (like in RPGs) are the focus for intrigue but any questions are quickly answered at the midway point of this volume.
I could be biased against this book, now that I think about it. I've been seeing a lot of the same tropes in similar books: Vaguely medieval setting, magic with few limitations, the adventurers' guild, an aristocracy, a prodiguous main character becomes strong in just the introductory chapters. There's something in those tropes that appeal to me and I'm hankering for something there that I can't define.
Maybe I just dislike the storytelling — the world is mainly fleshed out in exposition. Since Mercedes has read every book in her poor noble house, she has near encyclopedic knowledge. Any gap in the reader's understanding, she can fill. There's no sense of wonder or novelty because our point-of-view character already knows it all. And if she doesn't know it, she will conduct experiments that never fail. And if she cannot experiment, she will find someone that can explain in full.