Does this look like a mashup? I plan to read it because - well, leprechauns and Tir Na Og!
Click through the the website. You can get a leprechaun name, should you so desire. Also, watch a trailer.
It reminds me very much of the announcements that came with Artemis Fowl - the nemesis of leprechauns all over the world. Ronan's cadet-ish-ness makes me think of young Harry swept off to Hogwarts. With predecessors like those, this book has a very good chance of success!