Hopeless by Colleen Hoover

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Sky, a senior in high school, meets Dean Holder, a guy with a promiscuous reputation that rivals her own. From their very first encounter, he terrifies and captivates her. Something about him sparks memories of her deeply troubled past, a time she's tried so hard to bury. Though Sky is determined to stay far away from him, his unwavering pursuit and enigmatic smile break down her defenses and the intensity of the bond between them grows. But the mysterious Holder has been keeping secrets of his own, and once they are revealed, Sky is changed forever and her ability to trust may be a casualty of the truth