Wonderful Memory: Not Impossible

All the people in the world have become completely unparalleled. The special reason for this is their indestructible memory and excellent recall. To achieve this heritage, what efforts did people make, how did they adopt what it means, and at what doors did they stumble?

 Even if someone had a secret recipe or secret of memory, they would travel for months and ask at its doorstep, but often they returned without meaning because whoever knows the secret takes this secret to his grave. 

In such an era, there are a few people who have the passion and yearning to serve God's creatures. They live and die with the passion of serving the creatures. This book is the name of the spirit of service that you should improve your memory. What is the book?