I have some good ones for you - some more "adventure" than others, but all with a romantic subplot.
Sabriel by Garth Nix - In a mystical land, Sabriel takes up her father's duties as a necromancer who returns troubled souls back to the land of the dead. This duty requires her to travel to the realm of Death where she faces all manner of evil beings wishing to escape to the land of the living to wreak destruction. As a bonus, she finds unexpected romance along the way. The way Nix melds a recognizable modern world with one of magic sets this series apart from everything else
The China Garden by Liz Berry - When Clare goes with her mother to an English estate with dark secrets, she begins an unexpected journey. The ensuing story spins itself into many layers, featuring mystery, fantasy, and romance, all centered around an ancient family feud of which Clare is unwittingly a part. This novel is very rich in detail with a lot of historical and mythological references, so it is not for the faint of heart. For those who like deep stories with realistic romance, this is an outstanding read.
Cold Mountain by Charles Frazier - In a pseudo-retelling of Homer's Odyssey, wounded American Civil War soldier Inman decides to desert to return to his Blue Ridge Mountains home and his love, Ada. Inman's journey runs a gauntlet of physical and emotional challenges against marauders, bounty hunters, and witches. Meanwhile Ada tries to maintain her father's farm in a world gone mad. This powerful and moving epic will weigh on the reader's mind long after the final page is turned.
Down the Dead Road by David J. Nix - Teen "Cowboy" is pursued by Death, who has made multiple attempts on his life. He is an easy target, having lived on the streets his entire life, raised by a homeless woman. A series of events, including encounters with a supernatural figure, a brutal street gang, and a beautiful girl, lead him to search for his origins. The mayhem leaves both his heart and life in danger, but leads toward the astonishing truth. A story that gives humane treatment to the lesser of society, with a sweet romance thrown in. The multiple twists will leave you guessing.
Dustlands by Moira Young – In a post-apocalyptic future, 18-year-old Saba’s twin brother is stolen by black-clad riders. When tough-as-nails Saba launches a relentless search to recover him, she must fight for her life in gladiator cages, overcome enemies both creature and human, and learn to trust others for the first time. And try as she might, she can’t help but fall for the charming scoundrel Jack, who just may understand her more than she knows. The author tells Saba’s story in a raw first person format that blows you away.
The Forest of Hands and Teeth by Carrie Ryan - Seven generations have passed since the Return, a plague that reanimates dead humans into creatures that feed on the living. Teenager Mary lives inside one of the last enclaves of uninfected, protected by a chain link fence that surrounds her village. When the fence is breached, Mary flees the village with a small band of survivors. Their flight toward an uncertain salvation is both harrowing and revealing, as they try to determine if they are humanity’s last hope.
Tomorrow When the War Began by John Marsden - In a fantastic coming-of-age novel, Ellie tells the story of the invasion of her homeland of Australia by a foreign power. She escapes to the outback with six of her friends, where they make plans to fight a guerilla war against the occupiers. Ellie tells the story with superb sensitivity and insight, which generates the power that makes a good story a remarkable one. The relationships amongst the teens are incredibly realistic, and the accounts of armed conflicts are riveting.
The Shore of Monsters by David Nix - Five generations earlier, a horde of monsters nearly obliterated humanity. All males are dead or ruined by a monster plague; words like 'father' and 'romance' have lost meaning. When teenager Sky joins an expedition to the shore that falls apart, she must survive amongst the monsters that roam the ruins. She gets unexpected help from a very surprising source. Mystery, action, and romance follow!