Can I use only ITIL Manuals to study?
For Basic level foundation you can, as the ITIL manuals contain mostly everything you need. However it is not recommended as interpretations of ITIL may vary and can be different to that required or of the standard. Learning by an accredited course will save time and will give you a better understanding of the concepts.
For the intermediate or diploma levels it is compulsory to attend an accredited training course.