In order to get the room you want at the time you want it, you are advised to book in advance but - if you are willing to take a chance - it is not obligatory. Philip Robinson Library group study rooms can be booked online here.
In the Philip Robinson Library, individual study rooms are available on a first come, first served basis and are not bookable. YourSpace (Level 1) can be used by groups of Newcastle University students working on projects and presentations and is available on a first come, first served basis.
To use the accessible study rooms, you should book in advance but, if the room is free, you can make your booking on arrival.
The Walton Library group room is available to book here: http://www.ncl.ac.uk/library/about/study#walton