How useful is a CCRN certification for ICU positions? How long should you study before you take the exam?

It is a very challenging exam. But some institutions will give you addition money if you are certified, it will also bump you above other candidates if you are applying for a new ICU position

What is the best way to study for the CCRN? Is there any books? YouTube channel? Online or in person classes/programs?

The CCRN exam is challenging; therefore, a study period of at least 8-12 weeks of full focus is recommended.
The validity of the CCRN certification is to reinforce and maintain skills set and knowledge-based criteria for nurses who are providing care for critically ill patients in critical care and ICU units.
I also think that a specialty certification enhances ones competency to be able to implement skills that another cannot, which embraces a sense of accomplishment.
The certification is for a period of three years before renewal.
Hope this helps. Ena-Lorraine