Work is a process by which energy changes forms. It is a process . When work is done, energy changes forms. This means, really, that energy is being converted from chemical potential energy stored in your muscles to gravitational potential energy of the book - energy is changing forms. In other words, gravitational potential energy is being converted into kinetic energy - work is changing forms.
Work is the process by which energy changes forms.
Conversely, if energy does not change forms, then no work was done. If you carry your book across the room, the energy of the book does not change - no energy changed forms, so no work was done.