No, that headline wasn't sarcasm. I spent years as my neighborhood's go-to babysitter, and after hundreds of nights watching kids, I honestly believe that Terry Deary is using the correct approach in his Horrible Histories books. Kids are often a little more mature, and a lot more bloody-minded, than we give them credit for.
The Terrible Tudors approach, as with any Horrible Histories book, can be summed up as follows. 1) School is boring. 2) Teachers don't teach you any of the cool stuff that would actually make you care about the period. 3) Teachers are, in fact, out to get you. A little heavy-handed, but I've known a lot of eight-year-olds who were very firm on points one and three, and after encountering something like Terrible Tudors would be more than willing to concede point two.
This slim volume contains information on Tudor history, sports, games, medicine, food, religion, and royalty, interspersed generously with cartoons illustrating or commentating on the text. Generous attention is, of course, given to the gross and weird stuff: by opening the book at random I discovered that Henry VII ordered all mastiffs in England to be killed, people believed that witches could turn themselves into butterflies, plague sores might be treated by placing a newly-dead pigeon on them, and that Tudor football (soccer, as we uncultured Yanks call it) had no referees, no rules, and might end with a full-scale village-wide brawl. That kind of stuff tends to stick in your mind.
Terrible Tudors lost a star, though, for raking out the old Oxfordian theory and putting Kit Marlowe in the "did this guy actually write Shakespeare's plays?" role. It never actually says he did, but to be honest, I don't think it belonged in the book; the Oxfordian theory is less an interesting fact and more a "here's the weird stuff people might say about what might've happened but probably didn't," which is a little tenuous.
Overall, though, Terrible Tudors is an excellent example of what Horrible Histories is all about: strange, gross, cool stuff to catch kids' attention and imagination, and bring the past to life in a way a lot of school texts just don't. Definite recommendation.