Long tap the book item in the library. In the popup menu select “Add to favourites”.

There are 2 ways.

You can put your book files into Books directory on the memory card of your device. (Or into another directory defined in Settings->Directories->Book path option.) All files in this directory will be automatically scanned by FBReader library service.

Alternatively you can manually open book you want to add to the library from Library->File system section. The book will be opened and added to the library.

In the library, tap on book item, hold for a second or two, then release. In the popup menu choose 'Delete book' item.