Unless you feel that you must read every word that Robert B. Parker ever wrote about Spenser, you could skip Rough Weather and not miss a thing you need to know about the continuing characters. And you might like the series better if you did skip this book.
The good news is that Rough Weather has lots of humorous dialogue involving Spenser, Hawk, and Susan. Otherwise, the story would make you sea sick from its choppy plotting that combines a ridiculous crime scheme with ludicrous investigation methods. The bad news is that the dialogue opens little new ground for information or humor. As a result, many readers will have a hard time being sure this really is a new novel . . . rather than being a mélange of past novels stirred up to look like a tasty parfait, but containing ingredients that are not so delicious when combined.
What's it all about? In her late forties, Heidi Bradshaw has had three marriages to wealthy men and enjoys the lifestyle of a queen. Prior to an undefined special event on her private island, Tashtego, off the southern coast of Massachusetts, Heidi decides she needs a man around to make her feel better ("I want you to be the man I can turn to if I need something."). Spenser is the choice, and he agrees after Heidi agrees that Susan can attend.
Moving past the armed guards on the island for what turns out to be the wedding of Heidi's daughter, Spenser can't figure out what his role is . . . until he spots Rugar, the Grey Man who has been both an enemy and an ally, among the guests and wonders what's up. Rugar observes, "I hope we are not here in conflicting missions." Susan later comments, "It's as if Rugar has no soul."
Naturally, the issue is quickly resolved when Rugar leads an armed band into the wedding to kidnap the bridge and dispatch those who oppose him. A storm comes up unexpectedly, and Rugar cannot leave the island. Spenser decides that the best he can do is look out for Susan, and let Heidi, et al, fend for themselves.
But that doesn't end the matter. Wrong has invaded Spenser's turf and he feels responsible to sort matters out. Working with various police and federal agencies, Spenser gradually sorts out the reasons behind the murderous marriage vows.
Unless you aren't paying attention as you read, you'll figure out what the game is pretty early in the book. The only mystery will be why Spenser and the police have so much trouble. The answer might be related to the need to turn this weak story into something longer than a novella.
The worst news is that the book's ending suggests the possibility of a sequel. Yuck!