While we're on the subject, are there any other contributions to the Conan series written by other authors that are worth reading? I should I stick to Howard where attall possible?
There are some of them that you may find worth reading, but I'd be very careful. I have a fondness for them, I'll admit, but that's because I found them very young, and there's a large degree of sentiment there. Karl Edward Wagner's
The Road of Kings is rather good, though, if you can find it. A few of the stories by Carter & de Camp are not bad reads, though they're very uneven, and the majority are... well, let's just say, not comparable to REH.
If you really like them, you should try some of his other work, such as the Bran Mak Morn, Solomon Kane, or Kull stories; or the upcoming Best of, which is a mixture of all sorts of things. His stories of the Crusades aren't bad, either.
Bison Books (an imprint of the University of Nebraska) has got some of his books I'd recommend:
University of Nebraska Press
These will give you a pretty wide variety of things he's written, from his humorous Western tales to some pretty gritty regional work; from the supernatural adventure (and downright grim horror) to his oriental adventure and a hefty dose of his Crusade stories.