What is the difference between online journals and e-books?

Frontiers publishes articles exclusively online on a rolling basis. Every time a new article is accepted by the editor, we publish it directly and update the table of contents on our website. Articles appear on the journal’s main page with links to the full article content and images, accessible at no cost to any reader worldwide. 

Frontiers also publishes ebooks arising from Frontiers Research Topics, which bring together a collection of published articles around a focused theme, and which can be purchased and downloaded on the website.