by Hank Friedman
Astrology, Psychology, and the Four Elements (a fine introduction to the four elements, the cornerstones of astrology, but he simplistically equates the water signs with the water houses, which is not accurate.)
Astrology, Karma, and Transformation (excellent discussion of outer transits)
both by Stephen Arroyo
The Inner Sky (some of the best writing on the twelve signs.)
The Changing Sky (a very good introduction to transits and progressions)
Skymates (how to use astrology to evaluate relationships)
all by Steven Forrest
Astrology, a Cosmic Science (a great metaphysical astrology book by one of the best astrologers of the 20th century, occasionally too negative, e.g. on Venus in Virgo.)
by Isabel Hickey
Astrology, a Spiritual Science (out of print) (Great reference, a true labor of love, definitely worth trying to locate)
by Marcia Moore and Mark Douglas
It's About Time (out of print) (a unique and priceless Seth/metaphysical approach to astrology)
by Ned Johnson
Complete Astrology (very comprehensive)
by Alan Oken
Astrology (a good first book on astrology, sometimes titles "Teach Yourself Astrology")
The Planets and Human Behavior (The best reference on planetary correspondences)
both by Jeff Mayo
Astro-Essentials (A very good contemporary cookbook of planets in signs, houses, & aspects)
by Maritha Pottenger
Houses of the Horoscope (One of the best books on houses, very comprehensive.)
by Bill Herbst
Elements of House Division (The best --somewhat technical -- book on the basis of the different house systems.)
by William Holden
Planets in Transit (The classic book on transits, unfortunately doesn't cover the vital contribution to the effect of a transit that the sign the natal planet is in makes.)
Planets in Composite (The book that literally invented the Composite chart technique)
both by Rob Hand
Saturn in Transit (A very good book on Saturn cycles)
by Erin Sullivan
A Handbook for the Humanistic Astrologer (out of print?) (Wonderful examination of a vast array of factors in a chart, worth trying to find)
by Michael R. Meyer
Saturn: A New Look at the Old Devil (A superb book on Saturn, just don't buy her notion that houses equal signs, e.g. Saturn in the 5th = Saturn in Leo. Simply not true.)
by Liz Greene