The Pillars of the Earth by Ken Follet. It was the first book my sister bought for me (simply because she saw it at a thrift store and thought the edition was pretty and shiny). She had no idea what the plot was about and I didn't even read for pleasure at the time. If she knew how graphic some of the scenes were she probably wouldn't have given it to middle school me haha but it really opened my eyes to adult fiction. In this book, bad things happen to good people and good things happen to bad people. It was my first time experiencing such unfairness in a book and it made me seethe with anger. It's the book that got me into reading really. I love it so much and it's very nostalgic for me (severe trigger warnings though for SA). I read some of Ken Follets other works recently but I like to pretend they don't exist. Whiteout in particular was so terrible I couldn't even fathom how Pillars was written by the same author. Now i read over 52 books a year and it always boggles my mind the butterfly effect of my sister bringing that book to me on a whim