I know this sounds crazy, but sometimes, fictional characters become your friends. After plunging head-first into M.C. Beaton’s best-selling Agatha Raisin Mystery Series (Minotaur), that’s exactly how I feel about the blundering, self-absorbed, outspoken, middle-aged, sexually promiscuous, shop-a-holic, gin-swilling amateur detective, Agatha Raisin. What makes “Aggie” so appealing? Her misadventures…