My sister, who reads a lot but has seen little of any TREK, finally saw TMP this year and thought it felt like an adaptation of an Arthur Clarke novel.
As a big fan of ACC's work, I can appreciate that comparison. Of all the Trek films, TMP is the only one that can really call itself a science-fiction movie, the closest to various ideas espoused in literary sci-fi.
I often wondered what a Star Trek novel by Clarke would've been like, had he ever chosen to write one. It is a shame that this brilliant mind is no longer with us.