I thoroughly enjoyed this book, perhaps because I'm not dumb enough to think that the writer intended that you should actually tell these things to small children. I have two children (not so small now) both of whom found the jokes funny, particularly some which have a sly dig at parents (e.g. "Wine makes mummy clever")
I found the humour to be very much in the "Far Side" vein, in that it is slightly off-beat, and this may well be why my kids enjoyed it, as they also enjoy the Far Side cartoon books.