I would echo the other reviewer's observation that this is far superior to the Harry Potter books. Better writing, more imagination and a truly epic set of stories. If you've seen the lamentable TV adaptation, fear not, they didn't do these books one ounce of justice. I wouldn't say that these books are much like Tolkien, though; they're more sparingly and elegantly written.
Ursula Le Guin is a genuinely great writer and although these books are ostensibly the story of a wizard, from his childhood, through epic quests and acquiring the wisdom of age, the author uses the story to examine morals, language, politics, war, the roles of men and women in society and so much more. She presents a fully realised world with it's own races, customs, languages and mores.
The prose is lucid, elegant and clear; no words are wasted. I enjoyed 'A Wizard of Earthsea' when I was eleven - I was captivated by the world of Earthsea, thrilled by Sparrowhawk's quest and terrified by the shadow hunting him in the dark. Re-reading years later I was just as captivated, delighted that the book can still raise a chill but also amazed to find that I had missed so much detail in my childhood reading; missing, as I pictured the book that first time around, that so many of the characters are people of colour, for example.
A wonderful trilogy for children (older children or strong readers, probably) and adults alike.