I was playing this weekend creating Epub documents from one our school blogs.
The key to this is using the plugin Anthologize. Anthologise allows you to use blog posts to create, among other things, an Epub document made up of your blog posts. In addition, the plugin allows you to add information from RSS feeds of any blog to your document. The book I created was through the RSS feed of our Eportfolio8 blog.
I had some problems at first. Creating the document resulted in memory issues and white screens. I increased the max_execution_time and memory_limit in my php.ini and the plugin worked really well. Although the plugin is fairly easy to use I created a quick “How to Guide” on creating an Epub with Anthologize as a reminder for next year (section 4.2)
Tried this out with a number of posts from our Efolio 8 blog site (322 blog posts resulting in an 8.1 mb Ebook) to see how many posts I could add.