You can dive in and wade through the hundreds of pages of details in DSM-5 as you're preparing for the social work exam. It's probably more effective to take a quick stroll through the essentials. Just tiptoe through the diagnoses. To make that simpler, consider using the short Desk Reference version of DSM-5 for exam prepping. The big DSM-5 is just too much to digest. And the level of detail that lies within it is generally beyond what you're expected to have grasped come exam day.
To get and stay extra up on DSM-5 changes and exam-likely diagnoses, the web is there to help. We've linked to these helpful sites before: