I'm looking for a good book that will teach me general principles of exercise. I don't want to learn about any specific workout programs. I'm really just seeking to learn more about fitness so I can put together my own workouts.
I'm partial to Tom Kurz' Science of Sports Training. Supertraining is well spoken of. Part of the problem you'll run into is that this is an incredibly broad topic that can span multiple distinct research disciplines. Going from the high level overview down to the biochemistry will take a long time if you're just looking to put together a workout program.
The CDC physical activity recommendations and similar WHO recommendations are a good place to start for the skeleton of workout programming. I'd start from there and fill in the blanks with topic-specific books like Rippetoe & Kilgore's Practical Programming.
A few years back, while working on writing some fitness software, I came upon a book by Jim Bennett called The Weight Training Workbook. I was so impressed by the content that I decided to package it with the software. The book opens with a foreword by Bill Pearl former Mr. America, Mr. USA, and Mr. Universe.
“This no-nonsense book leaves little to the imagination. It covers all the basics and has everything necessary to start a sound fitness program. The Weight Training Workbook takes the guess work out of weight training and shows you how to design and track your training programs. It leads you through the do's and don'ts that are so important when striving to achieve personal fitness goals.”
That's followed by “The Basics of Weight Training” which provides all aspects of training including goals, equipment, specific exercises, designing routines, nutrition and much more. The book contains illustrations of all the mentioned exercises and includes a “workbook” at the end for designing a routine and tracking your progress.
Two other books that may be of interest were written by three time Mr. Olympia Frank Zane. Known as the "Zen" bodybuilder, Frank was not your typical bodybuilder as he stressed symmetry and pleasing proportionals over total mass. His books stress exercise programs, nutrition, psychology, dreams, meditation, motivation, and inspiration. The two I would recommend are Mind, Body, Spirit and The Zane Way to a Beautiful Body.
One book that's been helpful is Jim Stoppani's Encyclopedia of Muscle & Strength. It has information on core concepts, workout programs, and nutrition along with a handy list of exercises. It also breaks down how to organize your workout program for various possible fitness goals (losing weight, gaining muscle mass, and gaining strength).