I’ve listened to the first three book on audio and thought they were absolutely fantastic. Have I read book 4 or 5? Nope, because they aren’t available through Amazon yet. I just checked and I can purchase them through independent sellers, but that is a recent change. Up until recently they weren’t being sold in the U.S. I can’t wait to read them though! Book 3 ended with a major problem. I can’t wait to see what happens. So, if you know anyone that has them, grab them and send them my way. 
Skulduggery Pleasant is a detective and works for the magical community. He pairs up with Stephanie Edgley after her uncle (Skulduggery’s good friend) dies and leaves his mansion to her in his will. She stumbles upon the magical world and soon Skulduggery becomes her ally, protector, and mentor in all things magical. Together they fight evil, but always with an amazing amount of dry, hilarious wit!
I HIGHLY RECOMMEND the audios!!! Click HERE for the amazon link to listen to a sample.
There is a 6th book out too (released a few months ago). They are fantastic and they just keep getting better.
I use audible.com for my audiobooks (they’re owned by amazon now, I think), and http://www.bookdepository.co.uk/ for buying books non-locally. Both these places have all the books.
I second the recommendation for audio! This is a series I recommend all the time to tweens, teens and adults. I love the audiobooks!