I realize the supe store is still out of the textbook, and that really sucks. They have more copies on the way. In the mean time, just about everything you need to know for relativity can be found in Ch. 1 here. That is ... you have all you need to do the current homework set already. Also, this.*
If you still do not have a copy of the book, see me after class. I will either give you a loaner or make photocopies to get you through the next days, i.e., quantum behavior.
*You should always assume that professors recycle questions, and see if you can find content they used in previous semesters. Just use it wisely, or the exams will eat you alive.