When we say "There are some books" (or "here are some books") we are referring specifically to certain books, and so this requires an article. You could also say "there are Peter's books" or "there are the books you were looking for", "there is a book", "there is the book", etc. Always some kind of article.
When we say "There are books" it is a very general statement about all books ever, and so this sentence sounds incomplete. You could finish it, for example, "There are books in a library" or "There are books with pictures for children", "there are books for learning Spanish"