I have been dipping in and out of it for the last couple of years. Learning what I need to for certain projects. Ideally I would love to just sit down and learn everything in it from start to finish, unfortunately I just don't have the time.
More recently I have come across this:
A DVD box set full of Richard William's lectures to accompany the book. (You can preview his lectures on the link above.) I think it is essential for all animators to learn the very basics of animation. I have often found myself struggling when animating and just a simple look over of the basics just brings everything into place.
I am sad to say the price tag on this box set is quite high. It is understandable... but much too high for me to buy at the minute. I hoping that perhaps in the future I will be able to add them to my collection. For now I'll be just sticking with the book. :)