Came across this book recently at a local flea market - "Fundamentals of Astrodynamics". Great book explaining basic 2-body and N-body equations, classical orbital elements, and orbital transfer maneuvers. A little history is sprinkled in as well. Mine is a 1971 edition, but looks like there are still a few available on Amazon, new, old stock, I guess -

http://www.amazon.com/gp/product/0486600610?ie=UTF8&tag=outoftheeth-20&a...

Gets a little deeper than I want to go with some topics, but an interesting read, none the less.

Rich, N8UX