I thought The Fearful Summons was unrealistic. First off, who wants to read about a bunch of old geezers, trying to survive - yet another - action adventure?
I also didn't like the unrealistic story line of Kirk sleeping around yet one more time. Okay, it is consistent to Kirk's character I suppose, but realistic? come on. The aliens that this book introduced were mildly amusing - at best, but not very enjoyable to read about. They're just your average religious, primitive, four-legged freaks.
Lastly, this book was too wordy for my liking. I can't comment too much more because I tend to forget what I do not enjoy.