A blog can be a great way to get traffic to your website and the more visitors you have the better. You can of course try other methods of increasing the traffic to your site such as using paid for advertising, mass emailing or spamming other sites with links to yours. This can be expensive, time consuming and often has little results apart from the paid advertising, but eventually when your money runs out so does the traffic to your site.
By building a blog it allows you to add huge amounts of additional content without clogging up your main pages and navigation. It’s a chance to get some great key phases in to your site that people may be searching for and not only get your blog read but your main site viewed. If for example someone types in “what is the best book for a 5 year old” and you have written a post with that title then the chances are it may show up on Google. Within the blog post you can then put links in to relevant books that you sell to make it easier for the visitor to purchase the books they have just read about in your blog.