My current favourite books are the Temeraire series, by Naiomi Novik, partly because she is constantly *surprising* me, and I don't get really surprised by authors that often. Dragons. The Napoleonic Wars. A diverse cast of charactors, obtained in such a way as to never stretch historical credibility (though you do have to look at the series as a whole for that, and not book-by-book, especially the first one). What's not to like?
What's your current favourite book or series? (Other than Harry Potter.)