Kyuusen no Shima starts out quite promising. The first 3 or 4 chapters set the tone (mildly creepy and very "ecchi") and give a decent framework for the story to unfold. The premise (main character uncover misterious circunstances surrounding his family in a isolated insland) is also interesting. Sadly, it goes downhill fast, and the ending feels very rushed. There is some development of the main character and antagonist, but most of the support cast isn't really fleshed out.
Overall, if you appreciate ecchi manga (more like borderline hentai harem) and and just wants a quick read, this is a great pick. The art is very good and will keep you attracted to the manga, even when the story falters.