I read these books when I was about ten (many years ago now!) and still remember the richness of the telling. They ate books to stimulate the young imagination, enthrall, scare and lift the spirits in equal measure. I still remember the "dark is rising" rhyme and the (to a ten year old) startling realisation at the end of "Under sea, under stone" of who Uncle Merry really is. Deeper and darker than Harry Potter, they also avoid the predictability and formulaic plotting that creeps into Rowling's series. These books led me on to "serious" literature, drawing me on to read the whole series and triggering an obsession with books. A child who enjoys these would probably go on to enjoy Mary Stewart's "Crystal Cave" series when older, also Arthurian in basis and magical in the telling.