The setting also has a special appeal because the stories are mostly set in Michigan. The scenes and local references make me smile. (Do you know what Yoopers and Cudighies are? By the way, Chudighi is pronounced Coo' da ghee.)
My personal foibles aside, I found the books to be imaginative, well-paced, and fun to read. The protagonist, Isaac Vianio, is a libriomancer - a person who can manipulate the magic in books. In the first volume, Isaac reaches into Ann Crispin's book "Vulcan's Mirror," pulls out a disruptor pistol, and uses it to dispatch three vampires who want to cancel his library card permanently.
That got me thinking. If you could pull one item into our world from any book you've read, what would it be? Wonder Woman's Lasso of Truth? The cordial of healing from The Lion, The Witch and The Wardrobe? The Holy Grail? Harry Potter's invisibility cloak?