If you are an aspiring programmer who likes Minecraft then Project Orion is a fantastic way to get started. In my experience the singe most important factor in determining if someone sticks with coding is how fast they can make the computer do something. This course will get you actually making minecraft do stuff fairly quickly.
If your an experienced programmer from another language then it might be worth it just for foundations. Its less of a library and more of a framework, and it makes dealing with the spigot API significantly easier. It has cut down on the amount of time it takes me to write a plugin significantly.