If you are looking for libgen book download alternatives then you can go for Open Library which is similar to Libgen. So below are some features of Open Library:-
The books are arranged on digital shelves similar to a physical library.
It also allows you to buy content on rent and return it after reading.
It has several viewing options like one-page view, two-page view, and thumbnail view.
The language of the site can be changed to Español, Français, Deutsche, and others.