Hi SeeleahIt really depends on what your looking for, as in what area of astrology do you want to focus on.
I have a shelf full of astro books covering most topics - (except for synastry and composites), the ones I recommend are:
Predictive Astrology: The Eagle and the Lark by Bernadette Brady. Mainly focuses on transits, luminations and progressions. This is my absolute favourite astrology book, a real gem!!! It really got me hooked on transits.
Synthesis and counselling in Astrology by Noel Tyl. It's a big ass book that covers natal charts solar arcs, transits and progressions.
Secrets from a stargazers book by Debbi Kepton-Smith. This books aimed at advanced newbies - mainly deals with the natal chart.
The combination of stellar influences - Reinhold Ebertin(?).
This is another midpoint book (can also be helpful when looking at transits, progressions and solar arcs.) more of a reference text a bit dated, but still a good read.
Asteroid Goddesses - Demetra George
Does what it says on the tin! It's a great book that mainly deals with the big 4 asteroids and touches on some of the others.
Astrology and consciousness - Rio Olesky
A well written book that focuses on spirituality in the natal chart. It only deals with the signs, houses and planets but it's very in-depth.
These are just a few I'd recommend.
HTH