If any author has changed my life, then this is the one. I'll read anything he wrote, and have, except for a few of the more obscure boy scout books. I'm over the hero worship, but I'm grateful to him for exposing me to a few alternative points of view. Especially for describing rational anarchy in The Moon is a Harsh Mistress. A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly.
Specialization is for insects.
I have to admit to lapping up all the Callahan's books. I knew there was a whole dimension of magic out there for people who play instruments really well, with other people. Also, I wish Lady Sally's place existed. Lois McMaster Bujold She writes some of the best stories I've ever read. Excellent style and fabulous characters.