Bottom line - learn from the company manuals. A guide is just that - a guide.
There is no easy way to pass the exam but by study and being smart enough to know the subject material.
I have written many "guides" over the years for myself for various training events. They are obsolete the second they are written. Beware the amendment cycle.
Remember its not rocket science that is being taught here. It just takes a bit of work.
I wouldn't buy a guide from anyone - I would spend the time learning the subject matter myself. A statement that could be perceived as arrogant/cocky but at the end of the day I have to rely on only my knowledge in the event of an emergency - not the knowledge in some guide that helps me pass an exam.
Think about it.