It's not really a series, per se. There is another book published after this one by the same author called Queen's Peril. A quick goodreads scan shows that it is set before the events of this one (which is weird, but it's Star Wars and I'm convinced they're incapable of rolling anything out in chronological order).

Lucas might've been going for Roman parallels, but I don't think he got to the level of detail where it would actually make sense. I'm not sure anyone in 1977 thought it would be particularly popular.