1. Robbins & Cotran Pathologic Basis of Disease
Although mentioned in the MS1 book list, Robbins remains the definitive book on general pathology. I thought the book did an excellent job not only describing the underlying pathology of almost any major disease you can imagine, but it often clearly explained the physiology as well. Definitely the best reference book I bought and the one I used most often, especially when very detailed questions came up during pathology and immunology courses. The book also serves as the go-to reference when a detailed issues comes up during Step 1 and Step 2 CK studying. For a brief overview of topics, perhaps prior to Step 1, consider Robbins and Cotran Review of Pathology, 3rd Edition as well.
Regardless of whether your medical school teaches via an organ-based system or not, the second year will typically focus more on pathology and pathophysiology. There are many different books out there with regards to each system, but understanding renal pathophysiology will cover the majority of clinically relevant areas of physiology, including the relevant areas of cardiology. Renal Pathophys by Rennke, a Harvard Medical School professor is an excellent, succinct primer on the physiology of the kidney. The book's numerous diagrams and examples help clarify concepts that can at times be fairly subtle to grasp. The thing I appreciated the best was that nearly every questions I had was addressed somewhere within the book - pretty impressive for such a small volume!
While the author of this text Dale Dubin is covered many times on this site due to his hard-to-believe story, the book itself remains a good introduction to what an EKG is and how to interpret the various patterns seen. The numerous diagrams help clarify concepts that other books attempt to describe in text. While his writing is... unorthodox, to be charitable, his medical knowledge is correct and he does get his points across. The book is also a relatively quick read and has lots of white space for easy annotation. I'd suggest reading this later in the year as you start to ponder wards, and then updating it with copies of interesting EKGs as you enter the wards.
4. Pocket Medicine: The Massachusetts General Hospital Handbook of Internal Medicine (Pocket Medicine Series)
Like the book above, this is traditionally considered to be a "book for clinical rotations." However, I would argue that it is smart to purchase it early, during second year. Anytime you come across a common clinical complaint, such as chest pain, look at this book's section on it. The book efficiently lists fairly comprehensive differentials diagnoses as well as the next management steps that help you determine the etiology of the symptom or problem. Oftentimes, students in the basic sciences will have heard about various diseases and diagnostic modalities but do not have any idea how to sequence the different diagnostic tests. Pocket Medicine concisely and precisely defines each test and lets one know when and how each test should be used to diagnose a disease.
While technically this book does not relate to second year courses, USMLE Step 1 comes to dominate the second year, especially the latter half. As I have stated many times before, the trick with First Aid and Step 1 is to buy the book early and annotate it as you go through the year with additional facts or clarifying notes and diagrams. if you annotate the book as you go along, you will create this wonderful resource for yourself that you are intimately familiar with when it comes time to crack open the books to study for the boards.
While there are many other books to buy and refer to during second year, the five books described above should be essential for any medical student in their second year. The beauty of these books in particular is that you will continue to utilize them as you go forward in your medical career, both for directly learning about your patient's conditions as well as to study for board exams. Essentially, these are the books that keep on giving... giving the gift of concise, easy-to-access and understand medical knowledge.
If you have read Books For First Year Medical Students, and now this post, you are probably wondering about what books to buy for third and fourth year. Don't worry - keep your eyes posted here for those posts coming soon.