Without question, I would say my favourite books are The Bartimeaus Trilogy by Jonathan Stroud.
The Amulet of Samarkand, The Golem's Eye and Ptolemy's Gate.
If you had a checklist for the perfect book this trilogy would tick every box and more.
They're urban fantasies, set in modern London about magicians, parliament and demons. They're just absolutely fantastic. Stroud is one of the most amazing writers I have ever seen. (He came to my local bookshop once, and I missed him stressed emo ) The characters are unique and beautifully developed. The storyline is excellent, the plot is great. It is absolutely hilarious as well, without making comedy its main point.
I used to be an avid reader, but once I read those books I haven't read as much. These books are so completely perfect that there is no other piece of writing that could compare. Stroud deserves to be named one of the best authors on Earth, he really does.