So much reading….which of these documents is really important?

In a nutshell, all of them are. As a new student you would have received your acceptance letter, emails about orientation, registration, Student Services, the new student webpage and Cave Hill Online (CHOL) which all have important information and documents useful to new students, including the New Student Handbook and the various Faculty Handbooks. Each of these documents is relevant to you in some way whether it's your acceptance letter - which tells you the programme that you've been offered, your New Students Handbook- which takes you through the registration procedure, your Faculty Handbook- which gives the Faculty regulations and overview of the programmes, or your Departmental Booklet - which gives you more specific detail about departmental courses.