The second way to continue the book mechanization process is to design a new close vehicle for its contents. [..] Applications are fully interactive programs adapted to dedicated interfaces like smartphones, tablets or desktop computers. They can fetch their contents directly from the Internet and offer access to data and flux on the Internet, bypassing the web through more con- trolled and powerful user interfaces. [..] Because they offer clear boundaries, applications like books can be seen as containers. [...] Most contemporary voices condemn this lack of openness. Knowledge should be open, easy to share and link: the encyclopedia ideology. They rightfully point out that without open standards, ap- plication contents might rapidly become obsolete, impossible to read with standard hardware. [..] Book applications correspond to the second stage of the mechani- zation process, the mechanization of usages. By becoming applica- tions, books internalize their interactivity. [..] It would be an error to think that book applications are only rele- vant for hypermedia interactive contents. A book application allows designing the interactivity adapted to the goals and reading practices of documents as different as scientific articles, textbooks or novels. They permit to avoid the one-size-fits-all philosophy of the encyclo- pedia to offer specific solutions adapted to specific objectives. And of course they permit to invent radically new kinds of books: books that change depending on where or when you read them, books that learn as you read them, books that adapt to the news and other kinds of algorithmic books.