On a personal level the Selfish Gene by Richard Dawkins because it explained that "evil" is not evil but "mathematically" inevitable, thus allowing me to find (

On a personal level the Selfish Gene by Richard Dawkins because it explained that "evil" is not evil but "mathematically" inevitable, thus allowing me to find (relative) peace of mind. On a professional level The Mobile MBA by Jo Owen, because it explained to me - the programmer - valuable management skills in no bullshit way (I can not stress this enough), thus allowed me to grow in my career.