I just about wore out my copy of the original edition of this book years ago; i never got far into doing animation, but it really helped me to understand what i was seeing on the screen (as well as serving as a source of recommendations as to Good Things to look out for...)
While this may not be quite the essential text for aspiring animators that Will Eisner's Comics and Sequential Art (q.v.) is for would-be comics pros, it is a Very Good overview of the field as a whole, from techniques to materials to the creative aspects.
There is, admittedly, not sufficient detail on any one subject to take one to a true professional level, but there is sufficient detail and commentary to let the tyro make a beginning in almost any aspect of animation (within one's financial limitations, anyway -- while costs are rather less now than they were in the day when film was the sole practical medium of choice, some aspects of animation do cost more than others to do) and work at it enough to get an idea as to whether that's what she wants to do.
And remember -- you might not intend to make animation your life's work; but Mike Jittlov [Wizard of Speed and Time] was an accounting major who took an animation course because he needed an elective and it fit his schedule. The film he made for that course won him an Oscar nomination...
Anything can happen, and this book is a good place to check it out if you think animation might be one of the "anythings" you'd like to happen to you.