Anthologize is a free and open-source WordPress plugin that provides you an easy platform for publishing. You can grab your posts from your WordPress blog, you can pull in feeds from external sites, or create new content directly in Anthologize. Then polish, order, and edit your work, crafting it into a coherent volume for export in several ebook formats, including PDF, EPUB, and TEI.
Install and activate it then go to your WordPress admin area Dashboard > Anthologize and start compiling your project. Learn more at anthologize.org