When the price of the book is decreased by 15%, the total price decrease is 15/100*$400=$<<15/100*400=60>>60
The new price of the book becomes $400-$60 = $<<400-60=340>>340
The price of the book is then increased by 40/100*340 = $<<40/100*340=136>>136
The final price of the book is $340+$136 = $<<340+136=476>>476
#### 476