Cracking The Coding Interview A good book for refreshing knowledge before an interview. It is not suitable as a book for a comprehensive study of algorithms, but it contains quite good problems on various topics and solutions in several variants with detailed explanations.

Head First Design Patterns Easy to read and understand book about most common design patterns. At first, it may seem a bit too simple and kid-like, but just don't be rude.

How Linux Works, 3rd Edition. What Every Superuser Should Know Covers most important topics in Linux. Good to read after some experience in Linux.

Pro Git A good book for an in-depth study of Git if you already have some experience with it.