To the list of those penning books about the prez add the most authoritative source of all: President Bush. Insiders say that he’s been working on the project for a year. “He’s doing a memoir,” one insider says. “He’s keenly interested in it.” But here’s the odd part: Bush hasn’t actually written a word yet. Instead, he and his aides have been packaging the stuff he wants to reference so that he’ll be ready to write when the project moves into that stage. And that probably won’t happen until after he leaves office.