Comic Book Plus has a collection boasting over 42,500 comic books, all of which have been legally sourced, with almost 50 new titles being added each day. This massive collection is also entirely free. Besides the expansive collection, the site focuses primarily on books from the 1920s to the 1970s, meaning that it lacks some modern favourites such as Batman: The Dark Knight Returns. The site gives access to comic strips which are also from the 1920s to 1970s time period. Additionally, it has social features such as a forum for like-minded comic lovers from around the world to connect with each other. 
Log on to: comicbookplus.com

Comic Extra has a collection of comics ranging from Marvel’s Deadpool to DC’s Batman and Robin. However, a major drawback is that there are too many ads that distract from the reading experience. On the flip side, they have some extremely rare collectibles, like Amazing Fantasy #15, on the site for free, if you want to read a rare book, Comic Extra has you covered. 
Log on to: comicextra.net