Waves of nostalgia hit me whenever time travel novels come up, and I could talk for ages about the ones that stuck with me.
One of the books that knocked the wind out of me emotionally is 'The Time Traveler's Wife' — it's tender, frustrating, and beautifully messy because time travel is treated as a domestic, relational disaster rather than gleaming science. If you want a big, immersive alternate-history puzzle that actually feels like a detective story, '11/22/63' is my go-to: King's research-heavy approach to the Kennedy assassination makes the travel stakes feel enormous and personal.
For something older and foundational, there's 'The Time Machine' by H.G. Wells — it reads like an elegant allegory even now. If you crave mind-bending structure, try 'Replay' where the protagonist lives his life over and over and the moral questions pile up. And for an absolute gut-punch that uses time travel to interrogate history and identity, 'Kindred' will stay with you in ways few novels do. I love that each of these treats time travel differently — as romance, as thriller, as moral experiment — which keeps the genre endlessly interesting to me.