This is "The Essential Cosmic Perspective 6th Edition" in pdf format. Commonly used in astronomy classes in college. Even if you need a different version, this one should be the exact same as newer versions of the book that they want you to buy. All they do is change one or two words, and they classify that as a new edition. Don't fall for that trick. Just download this version and you'll be all set. Even if this isn't for a class, it is a very interesting to read.