Reddit mentions of A Better Way to Zone: Ten Principles to Create More Livable Cities

As an entry level planner you'd probably be staffing the counter and helping process land use permits, so customer service skills and professionalism will likely be pretty important. I got a graduate degree in planning and we only opened a zoning code for one assignment, where we looked at a property to see if a proposed use could be built given the zoning, etc.

So my recommendation would be to maybe find a zoning textbook (or A Better Way to Zone), look at the zoning code and recent staff reports from the places you're thinking of applying, and see if you can reach out to a planner there for an informational interview through the local APA chapter or just a cold call.

Books:

How Cities Work: Suburbs, Sprawl, and the Roads Not Taken by Alex Marshall

A Better Way to Zone: Ten Principles to Create More Livable Cities by Donald L. Elliott

Anything by Leon Krier (Architecture: Choice or Fate being my favorite) or William H. Whyte (The Social Life Of Small Urban Spaces being my favorite)


Essays:

Jane Jacobs and the The Death and Life of American Planning by Thomas J. Campanella

Toward and Urban Design Manifesto by Allen Jacobs and Donald Appleyard.