I have made some truly delicious biscotti - and some things which really should just be called "biscuits" or even cakes - based on the recipes in this book. But in every case I have had to work out for myself what to do. The book has been very poorly edited. The method is often vague, or omits to mention what to do with one or more of the ingredients, or just doesn't make sense - the best example was being told to mix a set of DRY ingredients to make a soft dough! Cooking times are generally way out. And I pity anyone who tries to use the bizarre American versions of the gramme quantities!
However, if you are prepared to use your experience to work with the ingredients given, then you should get some very authentic tasting biscuits that also look delightful.
A key ingredient, bitter almonds, are actually apricot kernels and can be bought from Julian Greaves (in the UK). They can be blanched by covering in boiling water for a few minutes then popping them out of their skins. I'm also inclined to use a slightly smaller proportion than stated in the recipes as the bitter almond flavour is very strong. But the end result is so much better than using almond essence.