It might. Let's take a look...
If your book educates readers about a process, helps solve a problem or demonstrates a new method of doing something, a blog could complement your book and help build an audience.
If you're thinking of offering online courses based on your book, a blog could help build your email list. If you're thinking of doing webinars, appearing on podcasts or coaching, a blog could be a useful complement to your book.
If you're active on social media, your blog could be the "command central" from which you build a stronger online presence.