One of the few books which brought a transformation in my perception was Ayn Rand's 'Fountainhead'.
Most fans of Ayn Rand consider 'ATLAS SHRUGGED' as a seminal book. However I found 'Fountainhead' appealing and more humane.
The character of Howard Roark was truly inspiring, so much so I wanted to follow his unwavering focus and his uncompromising attitude towards his profession.
Truly inspiring.