I bought a hardback (casebound) copy of Haanel's book and started reading it in my teens - some forty + years ago! The book image you see below is not that of the 2008 version I last read, but that does not matter. Haanel's book continues to be printed in numerous versions and languages, which is a testament to its continued need and relevance. As Haanel states:

"The 'Master Key' is here given to the world as a means of tapping the great cosmic intelligence and attracting from it that which corresponds to the ambitions and aspirations of each reader.

Divided into parts and subsections that makes for easier reading and comprehension. My advice? Read and digest slowly. Then, rinse and repeat - again and again! You'll gain something new every time.