The Dresden Files audiobooks in order

Which order should you listen in?

Read them in publication order. The early books are shorter and more case-of-the-week; the series gets substantially better from Summer Knight onward and most people who bounce off book one are told to push on to book three. There is also a novella, Out Law, numbered 18.5 and published in 2026, plus a run of separate "Dramatized Adaptation" editions of the early books — those are cast productions, not the Marsters readings, so check which you are buying.