The 2,000 Year Old Man shows no signs of slowing down: Mel Brooks has just signed with HarperEntertainment to write what the publisher is calling ''an anecdotal memoir'' about his five decades in show business -- from ''Your Show of Shows'' through ''Blazing Saddles'' to the Broadway incarnation of ''The Producers.''
''You have to jump on an opportunity to publish a comedy genius like this,'' says exec editor Mauro DiPreta. The irrepressible comic had this to say about the book deal: ''I have always been a huge admirer of my own work. I'm one of the funniest and most entertaining writers I know. And I just can't wait to read my book.'' He'll have to wait only until next year.