I'd recommend the U.S. Army historical series on the Korean war. Despite being an official account, it's a lot better balanced than other US historiography, plus it's available online Although print editions have wonderful maps that can't be overrated.

I'm also going to recommend Russel Spur's "Enter the Dragon" because it's one of the few english books that tries to tell the Chinese side of things. Although it's style is not very academic and may lack rigor. If we're lucky someone else will come along in this thread and give a better book for telling the Chinese side of things.

I did not totally find Halberstam's "Coldest Winter" great because it put no effort into North Korean (or South Korean) or Chinese sources. In general, I think U.S. Historiography over-emphasizes MacArthur centric drama and personality conflict. It seems to me that there should be more books in English telling the South Korean, North Korean, and Chinese sides of the story, but I haven't been able to get my hands on them.