Q: downloading audiobooks to iphone

I recently purchased an audiobook in itunes that is over 7 hours long. I was able to download it onto my laptop, but I cannot get it to properly download onto my brand new ipad or my iohone 6. It acts like it is downloading, but never shows up in the music app and when I return to it in the store, it has the download cloud symbol by it, as if it didn't download. I'm confused. Is it too large for those devices?