Book excerpt: The art of being truly funny is an undervalued one in these angst-ridden times, but it is an ability that acclaimed novelist Sarah Payne Stuart has in abundance. Her talents have never been on more glorious display than in My First Cousin Once Removed, a memoir--at once hilarious, personal and sad--of her extraordinary Boston Brahmin family, whose most famous member is the legendary poet Robert Lowell, the author's first cousin (once removed).