Firstly let me admit I am a massive Star Trek fan and so I had a definite advantage knowing all the characters inside out before page one. But even for the novice Science Fiction fan then this is still a great read. The initial situation Kirk finds himself in is believably portrayed and is a sound basis for the plot development. My favourite part relates to the outside interference of the planet Talin and how with only a little stretch of the imagination, it could relate to Earth today.
With the event of The Next Generation, DS9 and Voyager the characters have frayed a little around the edges but still retain their prescence even in written form. I live in the UK and this book was first published in 1991 over here. I have read it no fewer than 4 times in that time and regard it as my top Sci-Fi read and my number 2 read overall (No 1 is Jack Higgins - Storm Warning (Fiction)). Beam Up Scotty and make sure you get the book as well.