Every book requires some research, whether it be a contemporary or a historical.
Even if you only write about what you know, set your novel in your home town and ignore what's going on in the rest of the world while your book is taking place in it, you'll still need to know myriad details that will effect your plot and enhance your writing. Being a writer of historicals, I do my fair share of research. There are writers who research a book to death and others that clearly would have benefitted from perhaps a tad more. A bibliography follows this article including all the books mentioned and several others I couldn't write without. You will develop your own essential references depending on your settings, eras, and interests.