I think it's difficult, but possible, to create characters that a reader really cares about in this genre. Kresley Cole does it in the Immortals after Dark sries. Showalter herself did it for me in the Lords of the Underworld series, which I enjoy, but absolutely falls flat here.
I bought this bundle because of the great price on Kindle, and have only been able to force myself through three of the books. I just put it down after that and went on to read a few other things. While LotU is the same author and same genre (fantasy/romance), I just didn't enjoy this nearly as well. The characters aren't developed, the women are all one-dimensional virgins, and there's really no conflict other than contrived situations the characters find themselves in. I think I've felt more angst when deciding on a toe nail polish color than I felt when reading these books. Even the sex falls flat, as it seems all of the virgins in this world enjoy a good pounding for their first experience. Blech.
I will probably muscle through the last two books in the series, as I read a few books a week anyhow, but I don't expect to find anything better than what I've seen so far. For a better series by Gena Showalter, I absolutely recommend her Lords of the Underworld books. They're really fun reads with interesting characters. If you enjoy plot-less romance novels, then Atlantis is probably OK.