Thank you for answering me! I didn't expect such a detailed answer, it's very nice! It's true that the books of Agatha Christie are not always good. I just started my "path" in the study of this genre and her books, and I don't know as much as you do.
Some research says:
How Christie Wrote - "She spent the majority of time with each book working out all the plot details and clues in her head or her notebooks before she actually started writing... The most everyday events and casual observations could trigger the idea for a new plot. Her second book The Secret Adversary stemmed from a conversation overheard in a tea shop: “Two people were talking at a table nearby, discussing somebody called Jane Fish… That, I thought, would make a good beginning to a story — a name overheard at a tea shop — an unusual name, so that whoever heard it remembered it. A name like Jane Fish, or perhaps Jane Finn would be even better.” Meanwhile, Who is
Agatha Christie – the queen of crime says - The Guinness Book of World Records has proclaimed Agatha Christie to be the second best-selling author of all time. She comes in second after the Bard, William Shakespeare. With the honor of being the second best-selling author, Agatha Christie is also known for having the most widely translated number as her books have been translated into as many as 103 languages.
But some people don't like her. Some people do not like the writing style, and some themselves are the topic of her books and the presentation of an idea ...
Perhaps she is praised more, as what she did during the time she was alive and it was a "shift" in the genre of detectives and so on. If you compare it with other authors, it is very difficult. Everything has its advantages and minus. And at the same time, if we compare the plots of modern books, then I will prefer modernity (if we talk about Agatha, and not in general detective classics).