How Much For Just the Planet? may well not be what you expect in a Star Trek novel--although the reviews you're reading will give you a better idea. I for one didn't expect it from the back cover copy, despite being charmed by the first few pages, in which the food replicators serve oddly colored orange juice (electric blue) and Klingon battertoast (undress-tunic green) and interpret idioms as requests for food. I'm not really sure if the reason for that was ever explained, actually... Admittedly, it was my first Star Trek novel (perhaps fitting then that this is my first review), but the others I've read since then are generally less silly.
Yes, it IS rather silly, as its beginning with the replicator incident should probably indicate. As the back cover blurb suggests, the book is about the Federation, as represented by the Enterprise, and the Klingons arguing over a planet with vast dilithium reserves. What is only hinted at is that it's also an intricately plotted but farcical comedy of errors, complete with Gilbert & Sullivan parodies (however, not being very familiar with their songs, I wish, like another reviewer, that what was being parodied was clearer.) and overabundance of pink Vulcan-non-peppermint (n'gaan to be exact) milkshake. There is even something about it a bit reminiscent of Terry Pratchett's writing.
One of my favorite moments involves the "inflatable rubber starship" that is being discussed on the first page, and which is, of course, top secret, and the fact that a couple of mischievous youngsters have no idea what it is, but I'll let you discover that for yourself.
The reviewers who don't like the book seem to complain about inaccurate characterization and the outright silliness. While I wouldn't say it was the most evocative characterization, I didn't find it a detraction from the experience. However, because of this, and the nature of the plot, I don't recommend this book to Star Trek fans who insist on accuracy and serious science or who don't appreciate lighthearted dramatics, cultural references, and this type of comedy. To those who do, I hope you read and enjoy!