So what is the fascination?
For me, I think that Ireland is one of the few places in our scientifically-saturated world where it's okay to believe that magic still exists. Ireland resonants with readers and smart writers take advantage of that fact. Even Italian writers.
Irish folklore boasts not only leprechauns, but banshees, grogochs and selkies! Then, all you need to do as a writer is to tap into one of these faerie types and start spinning your story. Okay, so it's not really that easy, but the place holds great fodder for the imagination. Need more inspiration? Track down some Irish music. I highly recommend The Book of Invasions by a band from the '70's called Horslips.
And need I lecture you again on the genius of Van Morrison?
I didn't think so. ;)