Learning radiology from a book is like trying to learn how to ride a bike from a book. The only problem is that most formal radiology teaching is like trying to learn how to write a novel by watching JK Rowling type on a computer.
There are a number of sites out there that have tutorials on cross-sectional imaging. You should know the anatomy already, but review what it looks like on CT. Perhaps a quick review of the MRI that is actually ordered from the ED. Keep in mind what radiologists care about is not what we care about.
What you need to know from a practical point of view is the stuff that needs to be acted upon before the read comes in; from a legal point of view you need to know the stuff that is so obvious anyone should be able to pick it up. "The overnight radiologist read this forearm series as normal, but the arm is missing from the elbow on down!"
Your cases should provide the best teaching. Look at the imaging, look at the interpretation. If there is something that doesn't make sense, ask about it. If you are at a place where the rads immediately throw you out the door, you picked a bad residency. Do your homework first so you don't come across as a complete fool,
"This was read as a normal on CT, and the clinical course showed it was not appendicitis, but it sure looks like an inflamed appendix to me."
"Ahh yes, this is a rare combination, you have the normal anatomic variant of ....., combined with an artifact of ..... to make it look like that. Don't worry, you will likely never see this combination again in your life."