There are really only two orders that you should read or listen to these books in, that being chronological, or series numbered. Now there are a lot of other ways you could choose, and many of these books work well as standalone novels, but if you want my recommendation, it is Series Numbered> Chronological > others. The only exceptions at this time to the series numbered rule is the prequel should probably be read / listened to after you read Afterworld or you will lose part of the mystery, but Merlin's Crucible can be read at any time.

On that note, here is the series listed in Chronological Order. I will update this as more books release/near their release.