Not sure anyone can add anything new to this field since Harry Lorayne
Books since him are more homage and variations
(Practice, practice, practice is the secret sauce to get even close to the pros)
However, even in everyday life the PEG system and ad hoc Memory Palaces are worth the time to develop!
Thanks to Dellis, I discovered Lauren Tothero's memorizing technique
I cannot make the Tothero System work, but the technique feels as if it should have potential
Memorizing a deck of cards is a cool exercise for short term memory; alas no real breakthrough technique
All in all, this book is worth a look-see, and a sure buy if this book is your first memory book