an open book

:  having no enclosing or confining barrier :  accessible on all or nearly all sides

:  being in a position or adjustment to permit passage :  not shut or locked

:  having a barrier (such as a door) so adjusted as to allow passage

:  to move (something, such as a door) from a closed position

:  to make available for entry or passage by turning back (something, such as a barrier) or removing (something, such as a cover or an obstruction)

:  to make available for or active in a regular function

:  opening

:  open and unobstructed space: such as

:  open air

:  a set of written sheets of skin or paper or tablets of wood or ivory

:  a set of written, printed, or blank sheets bound together between a front and back cover

:  a long written or printed literary composition

:  derived from books (see ¹book 1) and not from practical experience

:  shown by ledgers

:  to register (something, such as a name) for some future activity or condition (as to engage transportation or reserve lodgings)

:  to schedule engagements for

:  to set aside time for