I'm not even half-way in, but so far I think this book is gripping, entertaining, not too dumb (misuse of the word pederast notwithstanding) and altogether most pleasing. It's not even over-gruesome yet, despite the subject matter. It being written by Newton's 'Principia' is a bit of a tricksy approach, but it gives us tongue-in-cheek passages outside the story which are just as much fun to read as Jennet's adventures. I shall be interested to see if I change my opinion as it goes along.
Note on 6.6.08: It has since turned gruesome even by my standards. Still enjoying it, though.
Thoughts upon finishing: Historically inaccurate, but mostly aware of it. Very, very entertaining, and only as gruesome as you would expect of a witch-hunt novel. The approach is satirical, and the book is occasionally laugh-out-funny, even as it argues for Reason vs. superstition (relevant enough in a time when "intelligent design" is graced with the title of "theory" in a classroom that should know better) and becomes downright frightening in its alternating depiction of witch-hunters as misguided fanatical lawmen (Walter and Dunstan) or sanctioned serial killers (Abigail); adventurous in its shipwrecks and "Indian" kidnappings, last-minute rescues and pirates; sensationalist in its court scenes and cons; and just a lot of fun.
Normally I would say steer away from anything to do with witch-hunting because you really don't want to know, but in this case, it's kind of worth it.