I want to open .IBOOK file in my application. My question is is it possible to do it cause my client want to make some iBooks using the iBook author and want to open them in Library Application which I am working on. And If it is possible apple will approve this application or if there is any other way.
I think what you require is : UIDocumentInteractionController Class Reference
iBooks has an undocumented URL scheme of ibooks, means you can launch iBooks with a URL like [NSURL URLWithString:@"ibooks://"].
But I think, UIDocumentInteractionController is the correct way to do this. It is the way Apple wants you to do it. Plus, using UIDocumentInteractionController has the benefit of letting the user decide what to do with the file.