Many teachers and educators are already using their own materials and content to teach topics. iBooks Author is a free app available on a Mac that can turn that content and material into an interactive book which can be viewed on any iOS device (iPad, iPhone etc)
Check out some of these examples of iBooks. The NUI Galway books were created by Students in the Scoil Oideachas in NUI Galway
Below is a useful online guide (provided by Apple) that will help you with any problems you are having with iBooks Author.