Primary Care Otolaryngology by Mark Wax is one of those great tiny books to just breeze through in an afternoon, regardless of your specialty. It has a great balance of brevity and high yield knowledge, specifically highlighting otolaryngology surgical emergencies and general ENT knowledge. The information is easily applied to a number of non-ENT rotations, specifically in regards to outpatient primary care, and reading x-rays. ENT topics in general are pretty straight forward: easy to learn and easy to teach, which means you look like a star med student when you point out a concha bullosa on a random CT in the emergency room, floors, or outpatient setting, and then explain what it means.
You can buy a physical copy, or get the eBook for free online through The American Academy of Otolaryngology Head and Neck Surgery.