Can You Recommend Any Open Or Closed Online Sites Where I Can Read A Large Number Of Books With A Flesch-Kincaid Professional Level Of Tough Readability?

[julliarder]

I am searching for such a books at the categories as literature, teaching/education, journalism/media/writing especially. In my plans is to start read a basic grammar books for the beginning, but i also need a kind of perfect picture of what i would be able to study in high level of the same way of development. Like something what i would be able to read if i will not stop learning ten years in a row—

[PsalmEquipt]

No online library allows you to filter its collection by FK Grade Level. However, researchers have analyzed texts across various collections, applied readability formulas, and generated comprehensive lists of results. The findings are often shared in the form of spreadsheets and CSV files that can be downloaded and reviewed. For example, a quick search for "Project Gutenberg readability scores" will reveal several relevant projects. 
These sources should help you generate your perfect picture of desired readings. Besides Project Gutenberg (gutenberg.org), you can find books for online reading at Standard Ebooks (standardebooks.org) and The Internet Archive (archive.org).