On a mn recommendation bought this book for ds1 (9). I left it on the side, intending to have a little chat with him first, then forgot all about it.
11pm last night I went up and realised ds2 (7) was still awake ... and about 2/3 of the way through the book! ROFL
It's a pretty thorough book, but at least there's no school today - so no parents to complain about him telling their children things they didn't want them to know yet