Been reading through the HP books while diving into Wastelands: Stories of the Apocalypse. SK's short story "The End of The Whole Mess" is really great.
"Fantastic Beasts and Where to Find Them" is a really good short read for HP fans. It's funny/entertaining, I highly recommend if you just want something to flip through in a day.
edit - I've read a few more stories in Wastelands, some good some not so good.
I started "The Amulet of Samarkand", the first book in "The Bartimaeus Sequence" trilogy. It's good so far, Bartimaues is quite the character. I'll be reading this series along with the HP series, switching each time I finish one of the books.
"You lack the requisite spine and testicular fortitude to study under me"
"You do not know the first note of the music that moves me."