Today, Del Rey has published a series of all of Howard's original works. And, it should be pointed out that these books are a must-read/must-have collection. Each volume has a nice introduction written by various Howard scholars (e.g. Rusty Burke, Patrice Louinet, etc.), several of the volumes contain Rusty Burke's Short Biography of Robert E. Howard, each volume has illustrations by various excellent artists (e.g. Gary Gianni), and Notes on the Original Howard Texts. If you stumble onto this post here at On An Underwood No. 5 and have not heard of these volumes, then you're in luck. Each book is listed below with the blurb from the back of the book describing its contents. I hope this post helps you decide that if you have an interest in Robert E. Howard, these volumes are a worthwhile investment. Feel free to click on any of the links and order the volumes.
[Listed in chronological order according to their publication dates]