HER ONLY SIN by Ben Stein (St. Martin’s: $16.95; 352 pp.)

Dear Cindi: Being that we made a blood pact in high school to tell each other about super books to read, I want to tell you about Ben Stein’s wonderful story about Susan-Marie Warmack of Silver Spring, Md., whose only sin was that she was too smart.

Now I know what you’re thinking, Cindi, but don’t worry. I identified with Susan-Marie right away and so will you, because the way Mr. Stein writes makes you forget all about dumb stuff like intelligence.

The story is told by this dorky guy named Benjy who went to high school with Susan-Marie and has always worshiped her from afar. Benjy doesn’t have a last name, but just between you and me, Cindi, I think he’s supposed to be Mr. Stein.

Anyhow, Susan-Marie is a whiz at every subject, especially math, so later on when they’re both grown up, Benjy gets her a job at the White House where he works for Nixon doing statistics on what kind of political commercials get the most votes. Susan-Marie does this great survey on where Nixon ought to stand in commercials to make people think he’s stable and trustworthy. She figures out that if he stands in front of a fireplace or on a nice porch, they’ll vote for him, but if he stands on the side of a road they’ll think he’s too sexy, because standing on the road makes people think of sex.

A movie producer named Paul Belzberg hears about Susan-Marie’s road thing and gives her a big job at his Hollywood studio where she takes over the advertising. Soon all his pictures are big hits because the posters show the star standing on the side of the road. Susan-Marie gets smarter and smarter until she’s running the whole movie company, which makes Paul so jealous that he starts plotting to have her assassinated even though she’s his wife by this time.

So help me, Cindi, Mr. Stein writes almost as good as Jackie Collins. He always tells you what people are wearing or driving or using, so that you know right away what they’re like without having to wade through all that dull stuff that Miss King back in our high school English class called “characterization.�

I mean he writes things like: “Susan’s XJ-6 . . . a young man in a Melendandri blue blazer . . . her Bottega Veneta briefcase . . . Sid’s silver 450 SL . . . her Du Pont cigarette lighter.� He even has somebody “snorting cocaine off a Porsche key,� but my favorite sentence comes in the fire scene: “Then I ran back into the beach house and wrote out a note on Susan’s Francis-Orr stationery. THE FIRE IS IN THE COLONY. WE HAVE TO LEAVE RIGHT NOW.� Mr. Stein’s people might not have much character, but they sure have nice things.

They know important people, too. Like they don’t just jog, they jog “along the beach as far as Louise Lasser’s house.� Mr. Stein uses a lot of real people in this book, like H. R. Haldeman, Goldie Hawn, Connie Chung, Jack Valenti, Norman Lear. I didn’t know you could do that in a fiction story, but I guess it saved Mr. Stein the trouble of making up people of his own.

Mr. Stein is so wise, Cindi, so wise. Listen to this: “The most haunting of life’s mysteries is simply that time, which seems indelible at the moment, passes and is gone.� That reminds me of the kind of thing Stella down at the beauty parlor says when she’s combing me out. I showed it to her, and she thought so, too. She said she’s going to write to Mr. Stein and tell him a thing or two about stealing her stuff.

And then there are Mr. Stein’s comparisons. You remember what Miss King used to say about keeping writing simple and how we should always remember that Bible sentence, “Jesus wept,� because it’s so plain? Well, Mr. Stein proves that she’s full of you-know-what. He writes that somebody “looked as if he had been dipped in sulphuric acid while his toenails were being pulled out.� That means the person looked very unhappy, Cindi. Even better is what he writes about Hollywood millionaires. They look like “Damascus street assassins in gold and tailored leather, perpetually on guard against a return to dusty souks and goat’s cheese.� Wouldn’t Miss King croak?

But the part that made me cry, Cindi, is when Benjy is researching Susan-Marie’s early life for an article and he says: “Every time I came upon an eighth-grade report card for Susan-Marie, I could see her there, and I fell in love with her again. Every time I read about her gym class accomplishments in tumbling or field hockey, I missed her the way a man in solitary misses daylight and voices.�

That proves that Mr. Stein writes for women like you and me and the men who love us. Poo on Miss King. Love, Staci