I gave it a five star simply because the books is simple and very effective at getting you to learn the "art" of quick calculation.
I looked at all the others in that field. Most of them teach you tricks for quick calculation. To do certain calculation you need to remember the tricks. There are dozen of them and you just get confused. This book do not used trick but teach you "number sense" ... and how to calculate from left to right with complex number. Beleive me, I was affraid of that kind of calculation and with that book I learned a lot!
I used it because I am preparing for interviews in management consulting. Case study need you to do lots of quick mental calculation. I am very good with complex calculation but mental arithmetics is something else.
BUY THIS BOOK ... very slim, but as said before, lots lots of exercise well made and improving in difficulty ... cant say more, its the book I was looking for.
Amusing, it was first published in 1945 ...