Ireland has a rich and colourful heritage of mythological tales that future authors have plundered for inspiration and ideas. There is nothing really wrong with this as the tales that were originally told and, most importantly written done and passed on are worthy of a modern interpretation or at the least some very heavy borrowing.
There are many examples that you can see in the world of Fantasy fiction and they have also influenced the myths of other nations as well. One other important factor is that due to the spread of the Irish around the world for work and to escape persecution they took the tales with them and presented them to a much wider audience. You only have to look at the celebration of St Patrick’s day to see the effect that they have. The parades and pub crawls along with the giving of ST Patrick’s Day Gifts is now a regular occurrence. If you want to join in then ST Patricks Day Gifts available here fit the bill.
What literature and Art has been affected by the tales of Ireland. The Ballet and Nursery Rhyme of Swan Lake as huge references to the tale of Children of Lir. The exploits of Finn MacCool are similar to that of Hercules (although that may be another example of the Greek influence) and in modern works the connections to the Gandalf and St Patrick can easily be drawn as the walking pilgrim sent to help the people.
If a tale features an Elf it is to the Irish folklore that you should look!