My number one factor of a good vocabulary resource is that it gives you an example sentence for each word. Simple sentences are simply the best way to acquire new words and grammar. Simple sentences are great because it gives you a much higher chance of comprehending a word, even without context.
By now you may have heard of Lingo Mastery. They have released a few books in various languages such as, German, Japanese, Russian, Italian, Spanish and have many different types of resources including, conversations, stories and vocabulary books. You can pick them up in physical or ebook form, the former of which is quicker and cheaper.
Here I will be reviewing the 2000 Most Common Korean Words in Context e-book. I was surprised to see that they had spread out to Asian languages after discovering their Italian content. If you would like to see all the content they have to offer click here.