I, and many others probably, think this is a tough question. There is so-o-o- much trade-off between your practical (flight lessons) and your written lessons. Each lends to the other. And each complements the other as you progress.

However, while you're in the "waiting room", some generalized reading surely can't hurt.

I would recommend "Private Pilot Handbook" by Rod Machado. It's thick, and maybe expensive, but a real wealth of knowledge while light and fun at the same time.

Have you decided on a flight school yet?  If so, ask them what they recommend.  Some schools do not care, but others base their curriculum/syllabus around some of the pilot kits.  To name a few:  1)  Jeppesen, 2) Cessna, 3) Gleim, 4) King Schools, 5) Sporty's.  You can locate these kits (usually come with textbook, FAR/AIM, logbook, written test prep, and some other misc items that are needed/used in the training enviroment.  The kits are usually $100-300 (depending on which one, and if you get CD/DVD or VHS tapes to go with them).

I would second the previous motion of Rod's book, as well.  If you go online to Sportys or King Catalog or mypilotstore.com or Marv Golden and I am sure several others, they will have books and DVD/VHS courses available with a brief description.  From instructing, I can tell you, you can never know too much.

If your situation is you cannot afford the time or money for actual "flying" you may still have time to get with an instructor a few times per month and get ahead of the game.  Start by learning about the planes they have and maybe do a "discover" flight in a few.  These usually can be had for about $50 for 1/2 hour.  With this knowledge under your belt, you can more tailor your learning towards a specific make and model (which you will have to do before you solo, let alone take the "checkride").

Good Luck!!
Brian

definately get the gleim book to help you study for the written test.  every question that can be on the written test is in the gleim book word for word.  i studied that thing hard for about a month and when i took my written, i knew the answers to a lot of the questions before i was done fully reading a question.  the gleim study guides are essential to help you pass every written and get a high score, you cant go wrong with them. 

i also had the jeppessen private pilot kit and thought it was veryu helpful.  your best bet is to do an intro flight like agbgng said and then just talk with some people at the flight school.  they can help you out and get you headed in the right direction and off to a good start.  you'll never stop learning when it comes to being a pilot, so the sooner you start the better.

also, you may want to get your medical before you start training.  saw a guy who was training at the same school i was at fail a medical because of some unknown health problem they found, he had paid and logged over 15 hours and spent over $500 on books/supplies/new headset, had to of been a horrible feeling, i felt aweful for him.  you will need it to solo so its not a bad idea to get it early anyway.
but good luck with your training and i'll be happy to help you out with any other questions.