I have heard some by borrowing from the library. For example, Imzadi was not all that good (IMHO) due to being abridged.
Made in 1992
, when most unabridged
audio novels - of any genre - were made mainly for hearing impaired people. And were extremely expensive for most people, even if you could find them.
Six months ago, I bought an ex-public library unabridged version of "Sarek", narrated by Nick Sullivan. A huge, now fragile, plastic box from Chivers Sound Library containing ten
cassettes. 879 min. Such products were simply not very commercial in 2001 - when I open it, at least five of the ten cassettes fall off their pegs and tumble out - and Simon & Schuster Audioworks didn't attempt to do such unabridged ST novels until CD technology came along. (So far, I've not managed to find 879 spare minutes to listen to it.)
By comparison, the audio book of "Sarek" that S&S put out was 180 mins, in a neat, slim package, narrated by Sarek himself, with an original soundtrack. And I loved it! Several times. Mind you, it was released way back in 1994, before unabridged novels were even popular.