The novelization for Wrath of Khan was written by Vonda N. McIntyre and published by Pocket Books at about the same time as the movie's theatrical debut.
My copy is from the first printing and was purchased on 22 June 1982. Here is my diary entry from that day: "Today I bought Star Trek: The Wrath of Khan. It is written by Vonda N. McIntryre. I took this as a good sign since I had read her Star Trek novel The Entropy Effect and enjoyed it emensley [sic]. I was not dissapointed [sic]. I bought the book at 12:26, had half of it finished by 3:10, and stayed up 'till 10:48 to read the final words. It was not exactly the same as the movie: a couple of sub-plots were added and the humour was not quite as crisp, but the book itself was very good, with great intensity and power -- characteristic of McIntyre's other S.T. adventure as well."