Just four days after giving their 6-year-old son Tanner a copy of 1,001 Silliest Knock-Knock Jokes In The World, Kevin and Jennifer Voskuil are already experiencing deep regrets about the decision, the Mercer Island couple reported Monday. 'Hoozere?' asked a bleary-eyed Kevin, trying to sleep on the living-room sofa as Tanner read him yet another joke. ''Orange you glad I didn't say banana?' That's a funny one. Run outside to the garage and tell it to your mom.' Jennifer, who has been treated to 762 of the 1,001 knock-knock jokes as of press time, expressed hope that Tanner can be weaned off the book and onto one that is less interactive. 'Maybe the Guinness Book Of World Records,' Jennifer said. 'Or the thesaurus.' 