As a fourth year medical student, everyone is concerned about not knowing enough in preparation to be an intern. Some people freak out and schedule all of these hard rotations as a fourth year medical student in hopes of being better prepared for their intern year. The reality of it is that one month of "on the job training" as an intern teaches you much more than any preparation you could have done as a medical student.
The same thing works for Radiology. No level of preparation that you can reasonably do during your intern year by reading Radiology is going to prepare you for your first year as a Radiology resident. The truth is, just like medicine, you will learn MUCH more your first month than you will trying to read all of your intern year about it. So just relax for now. You'll have plenty to learn for 4 years starting in July. It will make much more sense when you are actually doing it each day instead of reading about it now...which is a very inefficient use of your current time.
Next year at this time, you'll look back on things and be glad you didn't waste whatever free time you had during intern year reading radiology.
If you get any Radiology book during your intern year, get Fleckenstein's Anatomy in Diagnostic Imaging. It is a cross sectional and radiographic anatomy atlas. If your guilt will not allow you to do absolutely nothing, then spend a little time familiarizing yourself with anatomy. You are going to need that book anyway as a first year resident and as a second year when you begin to take call. Simply reading Radiology texts without the benefit of being able to regularly work with the studies is an inefficient waste of your time.
And FYI, over the next 4 years I can assure you that your program is going to tell you to read FAR more than anyone could reasonably expect to do. Our "reading list" given to us for each month rotation is rediculously long. You have to learn how to pick out which things to read are good and which ones are a waste of your time. Do this by talking to your upper level residents.