Although provided with a catalogue, the shadow libraries are not real libraries in the digital context, as they are not authorized. They are also known as Black Open Access.
The most popular are Library Genesis (LibGen) for e-books and Scientific Hub (Sci-Hub) for articles in academic journals.
Shadow Libraries is a book published by Joe Karaganis ant it is an in-depth reading on the subject that you can find here in Open Access.
The article of Francesco G. Meliti takes its cue from the book and adds other current themes. References: Le collezioni delle biblioteche al tempo delle Shadow Libraries, dei Predatory Journals e dei Big Five, Biblioteche oggi Trends, n. 4, issue 2 (December 2018), pp. 77-88, https://doi.org/10.3302/2421-
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