I, personally, love astrology books published by Llewllyn Publishing. (Look for the crescent moon symbol on the book) Llewellyn George was an astrological genius, although a bit dark and "unbuttered". He is one of the most important astrologers of our time, helping bring it back into the new age of enlightenment. I'd recommend every serious astrologer to have a copy of "Llewellyn's New A to Z Horoscope Maker and Interpreter: A Comprehensive Self-Study Course" by Llewellyn George.
Search Llewellyn's Astrology Books here
Also, another great beginner's astrology book is called "The Only Astrology Book You'll Ever Need" by by Joanna Woolfolk
The title is a lie, but it is a great introduction to astrology and chart casting, and is less technical than the "A-Z Delineator/Horoscope Maker" book I recommended above.
Another great book is "Parker's Astrology" by Julia & Derek Parker. The illustrations are lovely, and has a great reference section/ephemeride in the back section. It is quite easy to understand, and one that I will guarantee you will use frequently.
Hope that helps!