Created in 1947, "Advanced Animation" has often been called the best "how-to" book on cartoon animation ever published.
Found at ASIFA - Hollywood Animation Archive, they write:
Animation historian, Jerry Beck, whose excellent blog Cartoon Brew is in the bookmarks of just about everyone in the animation business, has been hunting for a first edition of Blair's landmark book for many years. He finally found a copy in a collection of material that belonged to legendary animator, Dave Tendlar. If you are familiar with the revised edition, you're in for a treat.
This is definitely worth checking out!