Spacecraft Attitude Determination and Control, edited by Wertz, is another classic. Used copies are available for around 35 USD, but new copies usually over 200 USD.
Orbital Mechanics by Prussing and Conway (of Laguerre-Conway fame) is also a very nice book, going into more details of advanced orbital motion, including some more modern methods.
But damn, aerospace engineering books are really expensive. I've spent a small fortune on these books.