Hanja are the Korean word/syllables that form the majority of Korean vocabulary and as such are essential for learning Korean.
This book contains over 400 of the most common Korean morphemes from Chinese.
From the book:
Korean morphemes (syllables) that have their roots in Chinese are called Hanja. This book is intended for the student of Korean vocabulary and Hanja. Often, the memorization of vocabulary is random and done on a word by word basis that makes the process difficult, if not futile. But what if there were components of the word that are used across multiple words and were easily understood. The learner could "assemble" the meanings of the words from their smaller parts. These components would be like repeating and recognizable pieces to aid in memorization and comprehension. Such an aid exists in the English language in the form of Latin syllables- co, per, ex, lux, able, bi,…and so on. These roots and morphemes can be of great help to learning English. Korean in turn has its own foreign roots in the form of hanja. And hanja is actually far more pervasive and detailed in Korean than Latin is in English, so can be of much greater aid.