Wow. Reese Witherspoon is consistently killing it with her book recommendations (first Crawdads, then Daisy Jones, now Paper Palace!). 
This book was a mix of Normal People (frustrating love story with a long-standing past), Crawdads (very nature-focused with easter eggs pointing to the ending throughout), and a little splash of People We Meet on Vacation (a dual-timeline that adds context to the current turmoil between the characters).
Despite the fact that Elle cheats on her husband, the author does such a good job writing that I also felt like I cheated on my husband, and also felt conflicted as to whether I should leave him for my one true love.
I absolutely adored this book. The ending was perfect and beautiful, but by no means a "happily ever after". It kept me engaged, but was still not an easy read. This would be a great one to re-read, knowing the ending!