I've never read anything of his other than the first dozen Tarzan or first three John Carter novels. I remember liking them but the Mars novels changed lead characters after the third one and the Tarzan books were good, but there were so many I just burned out.
Warning to you Real Steel. The first novel ends in a cliff hanger, you'll want to get the second one and have it ready and waiting. First two books were part one and two of the first story. Should have been one book.