So I'm about halfway through the audiobook and it's already my favorite audiobook ever.

Because it's not Andrew Robinson reading a book. The book is written in 1st person as Garak telling the story to the reader/listener, and Andy is Garak, and any imperfections in the narration (e.g. character voices) don't come across as Andy mis-voicing Quark, but rather Garak's impression of him because he really gets into the groove.