Read chapters 3 and 4 of The First Three Minutes by Monday, October 21.
Read chapters 5-8 of The First Three Minutes by Monday, October 30 (i.e., finish the main text of the book).
As you read The First Three Minutes, you should keep track of questions that you have, either things that you find unclear or further questions that the book raises. I hope that many of these questions will get answered as a matter of course during the class, but you should always feel free to bring up questions that arise from the reading, and I'll try to set aside some time specifically for this purpose.
Optional reading on Special and General Relativity is Chapter 24 of Universe, on relativity and black holes. If you have a different astronomy textbook, you could just look up relativity in the index and read the corresponding sections of the book.
While much of what I taught about relativity theory is based on things I learned years ago, I have also done a fair amount of reading and rereading in preparing for this course. The sources on which I have relied most heavily are
Relativity: The Special and the General Theory, by Albert Einstein, Crown Pub, ISBN: 0517884410
The Principle of Relativity, by Albert Einstein, et al., Dover Pub, ISBN: 0486600815
Subtle is the Lord: The Science and Life of Albert Einstein, by Abraham Pais, Oxford Univ Press, ISBN: 0195204387
The first of these is a semi-popular account of relativity theory, first written by Einstein in 1920 and updated and republished many times since. It is written at a level similar to that of our course, and if you want to read more about relativity it is worth trying. The second book is a collection of English translations of original scientific papers on relativity, by Einstein and others. I gave you copies of two of the papers from this book; most of the others are more difficult, although Minkowski's paper on space and time and Einstein's on the bending of light are at a similar level. The last book is a brilliant scientific biography of Einstein, one that goes through his scientific thought with astonishing depth and perceptiveness; it is the best scientific biography I have ever read. Unfortunately, it probably requires a knowledge of physics at the level of an undergraduate major (plus some knowledge of general relativity) in order to be worthwhile.
If you would like a more rigorous presentation of special relativity -- covering mainly the topics that we covered in class but at a more mathematical level -- you can find it in most freshman level physics texts aimed at engineers and scientists. There is, for example, a quite good discussion in my high school AP physics book, which I think has evolved into the book Physics for Scientists and Engineers, by Paul Tipler (at any rate, he was the author of my AP book). If you are interested in a more extended discussion of relativity, I recommend
Spacetime Physics, by Edwin Taylor and John Archibald Wheeler, W.H. Freeman \& Co., ISBN 0716723271
This book deals mainly with special relativity, but in a way that prepares the ground for general relativity. The popular book that I mentioned that illustrates relativity by fooling around with the speed of light is now available as
Mr. Tompkins in Paperback, by George Gamow, Cambridge Univ Press, ISBN: 0521447712
In addition to illustrating relativity, Mr. Tompkins's adventures illustrate quantum mechanics, atomic physics, and other areas of modern physics.
A more recent popular book that has good explanations of relativity at roughly the level we have covered and goes on to discuss the subjects of time travel, cosmic strings, the beginning of the universe, and the future of the space program is
Time Travel in Einstein's Universe, by J. Richard Gott, Houghton Mifflin Co., ISBN 0-395-95563-7
In a vein that is less scientific but more poetic, I suggest
Einstein's Dreams, by Alan Lightman, Warner Books, ISBN: 0446670111
This is a work of fiction, purporting to describe a series of dreams that Einstein has in the weeks leading up to his special relativity paper. Many of these dreams have obvious parallels to things that occur in special or general relativity, whereas others are more flights of fancy. I found the book imaginative and quite well written; with this class as background, you might find it enertaining reading.