I'm currently a 2nd year undergrad student. I have done introductory courses on Mechanics and Electromagnetism, with the corresponding maths required for them. I am trying to figure out where my interests lie in order to apply for Grad school next year (my degree is of 3 years). I need a list of introductory books (just talking about the field in general, for example, NOT a textbook) which are short, concise and cheap(!), and will help me see what lies in that specific field. The fields on which I require books are : Particle Physics Theoretical Astrophysics Theoretical Physics (this is a little vague, I know, but I'll just ask nonetheless!) Also, what are the other fields relating to the above ones I might not know the names of? Feel free to throw in any suggestions, even if not related to the above areas. After all, I do not know much, and I need to find out where my interests lie in this 1 year. Thanks!