It’s probably a toss up between the Discworld series and the Bobiverse series.

Shameless plug:
lemmy.world/c/bobiverse

Seconding the Discworld series, but specifying that while the Random House Audio version narrated by Nigel Planer is excellent- The newer version by Penguin Audio with Peter Serafinowicz, Bill Nighy and either Indira Varma or Collin Morgan are absolutely top shelf.

I was put off before I started them because I assumed it was the “Narrated by a full cast” type of thing which is usually terrible. This is one main narrator (either Collin or Indira if it’s a wizard or witch heavy book, respectively) and then a new voice for the “author’s asides” that makes you feel like Sir Terry Pratchett is telling you little secrets himself and then one special character gets their own voice actor who is just perfect and adds even greater depth to the magic of these books.

Bobiverse is also fantastic.

AND The audio version of Project Hail Mary by Andy Weir gets a little extra something by being an audio version. If you haven’t read that I recommend going in completely blind with no spoilers at all if possible, don’t read a single thing about it first.