You can reserve a Library room in Outlook. After checking availability, go into your calendar and find the day you want the room. Create a new appointment for yourself for the time you need the room. Go up to the top bar and find Invite Attendees and type in the name of the library room you plan to schedule.
Start with the word Library and add "Collab" or "Shared" or "Conference" - your room should pop up!
Now add any other invitees, and then type a short description in the Subject line. Notice that the room you choose automatically also shows up in the Location line. Add any notes or comments and click the Send button. Your appointment should show up on both your calendar and that of the room.