I have to admire the clever way Planer verbally distinguishes about twenty different characters, conveying class, species, age, gender etc. And he swaps rapidly between them.
Also he doesn't give the female characters silly high-pitched or breathy voices. Interestingly the sexy characters (Vimes & Angua) both sound as if they've got blocked noses. Not sure what that is supposed to convey.
I might try Stephen Fry reading The Prisoner of Azkhaban next, though it's quite expensive.