I have not read all of these, and I am only reiterating what I've been told or have seen.
Well, I've seen other people in the past recommend A&P, and those who have taken it before their program have said that it helped them a lot. Veneficus recommended to me Clinically Oriented Anatomy, which teaches anatomy with a different approach from other anatomy books I've touched. He also recommended coloring a coloring anatomy book in parallel. For Physiology, MrBrown would recommend Guyton's Textbook of Medical Physiology. A popular A&P book is Marieb's Human Anatomy and Physiology.
Before reading A&P, I think reading Chemistry and Biology will benefit you. For chemistry, I read General Chemistry 4th Edition by Hill, Petrucci, McCreary, and Perry. For Biology I read Biology by Raven, Johnson, Losos, Mason, and Singer. Both were recommended to me by Veneficus, and he posted it in his resuscitation experts thread. At UC Berkeley, they use Biology by Campbell and Reece.
Before you hit cardiac in your Paramedic program, a lot of people will probably recommend reading Dale Dubin's rapid Interpretation of EKGs "orange book". MrBrown might also recommend Lippincott's 12-lead ECG interpretation "little brown book". I also learned that rhythms and 12-leads can still be intimidating after you've several books on it and feel pretty confident in it (Tommerag tested me on it, and it turned out I was all talk and no game). You can practice interpreting on TomB's website ems12lead.com, which also contains an excellent guide to axis determination, and buying a book with a bunch of rhythms with annotations on it (e.g., ECGs for Emergency Physicians 1 & 2) will help you adjust.
For pharmacology, I've been recommended Pharmacotherapy: A Pathophysiologic Approach.
Other books I've been recommended is Bates' Guide to Physical Examination and History Taking, Robin's Pathologic Basis of Disease, and Janeway's Immuno, and Clinical Microbiology Made Ridiculously Simple.
As a reference, I'd also have a dictionary-like Signs & Symptoms book (I have Lippincott Professional guide to Signs & Symptoms 5th Edition) and a Physician Desk Reference (PDR, I have Pearson Nurse's Drug Guide 2011).
From what I have heard though, all of this would probably overkill for your Paramedic program, and I doubt you'd be able to read most of them before hand (you'd probably be able to read Dale Dubin's book though, I read that in like a week). The S/S book and PDR might be useful, but it could probably be replaced by flashcards on what is introduced to you via your program. You could probably get a head start with AHA ACLS, or other alphabet soup certs. If you can get a reading list/syllabus from your program, it might be wise to get started on those.
Here is a list Brown compiled:
Guyton's Textbook of Medical Physiology
Cecil's Textbook of Medicine
Harrison's Internal Medicine
Rosen's Emergency Medicine
William's Obstetrics
Clinically Orientated Anatomy
Current Medical Diagnosis and Treatment
Lippincott's Textbook of Cardiovascular Medicine
Dubin's Rapid Interpretation of ECGs
Lippincott's 12 lead ECG interpretation
Bate's Guide to Physical Examination
Pharmacotherapy: A pathophysiological approach
And from Veneficus resuscitation experts thread:
Biology, Raven
General chemistry, Hill
Organic Chemistry, Wade
Molecular Biology of the Cell, Alberts
Biochemistry, Garret and Grisham
Physiology, Guyton
Robins Pathological Basis of Disease, Kumar
The developing Human, Moore
Fundamantal Neuroscience, Oswald
Pharmacological basis of theraputics, Goodman and Gillman
Principles of Internal Medicine, Harrison (as if there was another)
(for the ped's folks add Textbook of Pediatrics, Nelson)
Miller's Anesthesia, Miller
Here's also some links that might be useful to you:
Dr. Bledsoe's website -
http://www.bryanbledsoe.com/handouts
TomB's website -
http://ems12lead.com/
The EMT Spot -
http://theemtspot.com/
JPINFV's website -
https://emtmedicalstudent.wordpress.com/
I like to do little things like look up "what are the top 10 perscriptions", search Youtube for biochemical pathways of whatever, and look up research (especially on hot topics e.g., oxygen administration, c-spine, and using an NPA when there is significant craniofacial trauma). Don't be afraid to use your Google ninja tae kwon do samurai James Bond skills.