The Welsh Book was written by famous Welshman Roald Dahl (strong Welsh name, that) which is why it is referred to as The Welsh Book. Obviously I can't tell you the name but it sounds a bit like The Vitches.
The book is cursed as it contains real spells cast by the evil antagonists in it. If any author says the name of the book they will have their work refused by agents and publishers from London to Wigan. Their pens shall run dry; their paper go all crispy and yellow; their computers will take ages to start up; wine will turn to blossom Hill in their mouth; chocolate will become like rice crackers to them.
So never say the title of this book. If you do say the title your only hope is to quickly do the cleansing ritual below:
Turn three times on the spot,
Bend over and spit between your legs,
Chant, "Witches, witches, can't get me, you all smell of poo and wee."
It might work, it might not. But that's the best I can do for you.