An author website is your focal point for readers to keep in touch with you, to find your book promotions and find out what your getting up to. It is a 24 by 7 resource for readers that you have full control over and can update, with everything you do.
If you depend on social media networking to take the place of your website, this may be a strategic disaster as it places you at the whims of another party. Large organisations do fail and fall by the wayside or just come unpopular to users. Take Yahoo and MySpace for example and when they do you have to start all over again somewhere else. Another reason is that you can't control what Facebook or social media hubs will do with the design, with your likes, followers, or with its functionality. They do not offer any way to download or backup this data.
A good website gets stronger with you over time and is an investment in your author career that can return great financial reward. Your site puts you directly in touch with your readers.
So How To Go About It