What was the last book you read that just made you happy? If one doesn't immediately pop into your head, I suggest checking out In Other Lands by Sarah Rees Brennan. Though it started a little slow for me, pretty soon I was so in love with the characters and so invested in them that I didn't want it to end.
In Other Lands introduces us to Elliot Schafer, a bratty 13-year-old redheaded know-it-all who happens to be able to travel between worlds, which earns him an opportunity to go to school in the Borderlands. The Borderlands is a land similar to ours, but with much less technology and a lot more fantastical creatures. Here, most students study to become soldiers that guard the Borderlands, and a few, like Elliot, study to be the Borderlands equivalent of politicians, striving to keep peace among the creatures that live in the land through diplomacy. Elliot is not immediately a likeable character, but his snark is hilarious, and seeing this new world full of elves, dwarves, mermaids, and more through his eyes is delightful.
Elliot doesn't have many friends back home in the "real" world, and he doesn't find it much easier to make friends in the Borderlands. He eventually finds a place with two other outsiders, a beautiful and fierce elf named Serene-Heart-In-The-Chaos-of-Battle, whose shock at human gender norms and penchant for violence continually amuse, and Luke Sunborn, the golden boy of the Borderlands who excels at everything he tries. The book follows Elliot and his friends through their years at school, as they come to understand what they mean to each other and who they are as people. It's not an action-packed plot; it's a lot quieter than your typical fantasy novel, and that's what I found so lovely about it. It's more of a coming of age story that happens to take place among elves and trolls. It's also one of the best LGBTQ teen novels I've ever read, as well as being laugh-out-loud funny. I'd highly recommend it to fans of fantasy, but also to anyone who loves Rainbow Rowell or John Green, or anyone who's looking for something funny and clever, or anyone looking for a tender but not sappy love story... there's something for everyone here.