I’d describe The Dark is Rising series as a mix of Tolkein (Lord of the Rings series) and Lloyd Alexander (The Black Caldron series) with difficulty level between the two series. Also, I’d describe it as mix of Harry Potter and Percy Jackson, again with difficulty level between the two series. It’s an epic series pitting good versus evil and light against dark with the epicenter around an 11-year-old boy named Will Stanton who is the last of the six “The Old Ones” who are time-travelers and protectors of the world. The time traveling aspect is great because it introduces English history amidst a backdrop Celtic lore.
Lloyd Alexander’s The Remarkable Journey of Prince Jen reminds me of Percy Jackson but the zen version or even a more swashbuckling version of Where the Mountain Meets the Moon. For ages 8-14.