I've just read 'Inner Engineering' by Sadhguru in which he touches upon the different kinds of Yogas.  First of all he mentions that you need a guru to guide you in the path of kriya as it is a path that emphasizes on the mastery of your body energies and its mechanics, hence you need someone to show you as opposed to gnana yoga for example. Second of all he mentions that you need to be initiated into the kriya, otherwise they will not 'work' when you practice and may take you many lives to get 'liberated'. He specifically mentions not to learn it from a book as we do here on actualized.org.   Although Sadhguru is the real deal Gurus are renowned for being biased towards their traditions. I've been seeing tangible results with kriya and will continue as its the best tool I have so far but I'd like to know if it's viable for awakening.