Nicole Richie's The Truth About Diamonds (ReganBooks, $23.95) is a thinly veiled novel about a ''rock royalty princess'' in Hollywood. Regrettable Quote ''I always thought Lanny was nice to a San Andreas fault.'' Possible Reference to an Ex-Friend ''Simone was good at...airing her dirty laundry in 'home videos' she and her boy toys liked to make.''
Paris Hilton's Your Heiress Diary (Fireside, $18) is a thinly written ''diary'' composed of quotes from Paris, pictures, and lots and lots of blank space approximately 75 percent of the ''book,'' in fact. Regrettable Quote ''One of my heroes is Barbie.'' (Yes, that Barbie.) Possible Reference to an Ex-Friend ''If people aren't nice to you, they're jealous.''