Embedded System is directly related to the microcontroller. So you should have at least knowledge on one microcontroller (8/16/32 Bit). Presently most of the embedded professionals are prefer to write the code in C language. So you should have a good knowledge on C. Instead of C if you know the some other languages like: - C++, Embedded C, Assembly and ADA, it will put very good impression on Interviewer.
Books to Read>
1. 8051 controller by Mazidi
Practice all the exercises not leaving a single example
