Harry Potter Series, by J.K. Rowling
This series is a bit of problem for some people... Many parents, with understandable concerns, prohibit their kids from reading it. It is full of magic, and the main characters are wizards and witches, and this is an issue for a lot of Christians. That is absolutely your decision, and there are many other books in the world to read.
These books are brilliantly written. The balance between character development and plot is very good, especially in the earlier books (the later ones do drag a wee bit). The characters are very relatable, and and it set in a very charming world.
One of the main things to keep in mind is that the books do grow older. They follow Harry through his teen years, (11-17) and each book has him a year older, and progressively becomes writing for an older audience. The earlier books (until book three) are totally appropriate for a younger audience. Book four, The Goblet of Fire, starts bringing in some romance factors generally reserved for teen books (such as dating), but is still fairly clean.
Book five, The Order of the Phoenix, is (in my opinion) the worst book. Harry suddenly becomes quite a nasty, self-centered character, who enjoys hurting people, which, while totally understandable as a result of what he is going through, is not a good role model. On the other hand, there are some relatable situations of heartbreak, and grief, which harry and his friends have to go through; many more than your average teen. These situations, and the way they are dealt with, are very realistic and handled well by the adults in the series.
In the last two, Harry grows up quite a bit, and is started to be seen as more of an adult figure than child. There are definitely some really good morals running through the series, such as protection, love, friendship, courage, teamwork. This is an epic fantasy that is clean, (albiet, some violence), and a tender story about the depths of love. As a christian, a lot of the morals are in line with biblical principals. The magic itself is not evil, only the evil characters of the story use it badly, and it is quite clear when that is the case.
The magic/witchcraft in this book is no worse than any fairytale story with an evil character.(Snow white, Sleeping beauty, Hansel and Gretel, Alice in wonderland etc.)
All in all, about 8.5/10. Age recomendations 11+ for the first three books (Philosoper's Stone, Chamber of Secretes, and Prisoner of Askaban), 13+ for all the others