This is the first book of White’s magnificent 4-book collection entitled the Once And Future King, an epic retelling of King Arthur legends. In this first book, the young Arthur (nicknamed Wart) is tutored by Merlyn so much magic is involved. Lessons frequently involve Wart’s transformation into different animals: fish, birds, a badger, etc. There are also some gut-busting hilarious illustrations of the difficulties of jousting. Imaginative writing is coupled with impressive knowledge of natural history (how to fly, how to swim) makes this an enchanting read.
Amy adds: still laughing at the jousting descriptions!
What if you found an old mis-shelved fiction book in a University Library that contains an incident from your own life, described in perfect detail? This is the beginning of this wildly inventive novel and it gets better! Doors are painted on surfaces that become portals to an underground maze of tunnels and rooms filled with books/stories. Characters in reality interact with characters from stories, and time is very flexible. But this magical place is under attack and great quests ensue. Morgenstern’s writing is wonderfully imaginative; previously she wrote the fabulous 
This is a wildly imaginative book: where to begin? For starters, there is an Epiphany Detective Agency, a Library of Blank Pages and clever acronyms like NEED (Never Ever Enough District). The story is philosophical with questions about the function of the human heart (spoiler alert: true love) and the downside of hope. Overall, a magical read.
Note: The Magicians trilogy by Lev Grossman is from a list of recommended books about magic by Erin Morgenstern, author of the fabulous The Night Circus. More than half of this first book is about a magic school but this is not Hogwarts: the school is in upper New York state and the students are older (post-high school) so they indulge in young adult activities like drinking and sex, making for complicated relationships. There are two difficulties: learning magical incantations is very hard (wands are for sissies) and there is an existential dilemma – what is the purpose of magic in a modern world? This latter issue is addressed by the young magicians entering a fantasy realm, one described in fiction books and thought to be entirely imaginary; all the magicians have read the books about the magical world of Fillory when they were young children. This is where imaginative adventures occur with violence and a significant body count. So this book offers a very different treatment of magic compared to Harry Potter books, but is equal entertaining.
Book two of the trilogy, the continued adventures of Quentin and colleagues: more travel in a quest to locate five magical keys. Part of this travel is on Earth, using portals that are created precisely with Google Street View! And there are deliciously old-fashioned sea trips in Fillory. Much of the book has metaphysical tones. Where does magic come from? Are there all-powerful secret magicians (aka Gods; I was reminded of the Old Gods in Neil Gaiman’s 
The final book of the trilogy comes to a satisfying conclusion. More magical quests on Earth and on Fillory, with reappearance of some characters from books one and two. About 12 years have passed since book 1 and the consequences of doing magic and experiencing great magic has changed the magicians, bringing a world-weary maturity. This series is wonderfully imaginative. However, the 3 books need to be read sequentially; none are stand-alone stories.
This is a YA fantasy story set in medieval times with dragons, etc. Tess is a 17 year-old misfit, an obnoxious headstrong anarchist-in-training who invariably chooses to behave in a way that produces trouble and discord. Because of particularly scandalous behaviour, according to the norms of the day when women are supposed to lead constrained and subservient lives, Tess leaves on a journey of discovery, a pilgrimage of sorts. She is accompanied on part of this journey by a quigutl, a flightless sub-species of dragon (readers should consult the Glossary at the end of the book). Surprisingly, the story then becomes quite introspective about the nature of bad behaviour and finding one’s ash in the world, and thus more interesting than the average fantasy story. Overall, a very fun read.