Mr. Jerry Jon Seller's book, "Understanding Space" is an amazing textbook about the technical aspects of space. The text is well written, the diagrams are easily understood, and the "tech-factor" for space geeks is acceptably high. It is no wonder that the United States Air Force has recommended "Understanding Space" as its baseline text concerning Technical aspects of space flight.
For those afraid of "rocket-science" level math, the book is written at a very easy level, using algebra, trigonometry, and bits of calculus covered with a whole BUNCH of physics. It is an excellent text for technical classes, and also easily readable for non-technical space classes. I've personally referenced this book in *EVERY* space-related class I've taken (4 undergrad and a *whole* bunch of graduate classes) - if you buy it, you will use it, I guarantee.
The only downside to this text lies in the fault of its users, not the author or publisher. This book was written to be the introduction to the Space Technology Library, a list covering more advanced topics in space. That said, the text is written at a high-school/undergraduate level for math and physics; yet the USAF has committed its "Certified Space Professionals" to using the text at their advanced level "Space 200" course. If you're taking (or teaching) space-related classes, understand the level of information you're needing - there *are* other space technical books (some by the same publisher) that will cover these topics in more depth (i.e. harder math and physics).