Most things have proper in-universe explanation, although some take a while to get told to readers because the exposition is as much to the reader as to Myne herself.
While she has high magical power, it results in her having extremely frail body, and ironically she can only get as much magic power as she had only through her circumstances, if she was born in a better off family or a noble one, she wouldn't have grown to be this strong.
Her knowledge from Earth IS seen as abnormal, but very few people push her for the truth since they are aware she'll be wary if they ask about it, and profit > some personal secret in most characters' eyes.
And the people who do know decide to keep it to themselves.
Since her desire is for books, something that requires an industry to constantly make, she had to rely on others to run various workshops to make her books.
It's a series that goes at slice-of-life pace but with actual, constant progress instead of 'we spent a whole book for 3 days' some slice of life do.