How can I buy the VolcanoEbook?

Download it from the Play Store.

How do I read the books?

You can use it offline.

Why do I need to pay to read the books?

There are a variety of reasons. The most important reason is that you need to spend money on the app. That money helps support further development of the app. You can also get access to certain functions, such as accessing your cloud bookshelf or getting the most popular books in the category you like.