In Book Creator for Chrome, a teacher can create a library and invite students to join.
Each teacher starts off with 1 library that can accommodate 40 books (more libraries and books are available if you upgrade to a paid subscription).
Creating your first library
Click on the Libraries button in the top toolbar (by default it will be showing the My Books library - your personal library).
Click Create a new library. You'll need to give the library a name, and you'll see the options for whether or not you want to allow students to access the Google Image Search within Book Creator, and whether or not students will be able to read each other's books.
When you're ready, choose whether or not you want to invite students immediately or later. If you click on the button that says Invite people to library then you will be given a code - this is the code that students will use to join your library. You can also choose to generate that code later on, if you prefer.