I found this guide to building sand-castles/sculptures both clear and practical, and have no hesitation in recommending it for anyone whether 8 or 58, beginner or old-hand at sand carving (though not expert). It's pretty too :)
As to what it is that this book does right, I have to first explain that I'm a complete amateur at this (unlike the author) - I've entered a few sandcastle competitions but mostly I just make them for fun on holiday. And like others who dabble, while I have enjoyed carving the sand with a variety of equipment from the kitchen and shed, I've wondered whether there were better ways of preparing the sand than making a big pile and then squashing it down.
Well, that's one of the major ideas that this book gets across with plenty of pictures and simple directions: how let water and gravity pack your sand much more solidly than any stomping ever could, starting small and working up to how to create huge masterpieces similar to that pictured on the cover.
Other practical advice includes common design features, what tools to use, how to construct gravity-defying effects like arches, and how best to let kids get involved without destroying the more delicate bits.
And it works! I finally found the time to get out and try some of the techniques suggested, and it really is a revelation how much more details you can carve with hard-packed sand.
Good sloppy, sandy, sore-kneed fun.