Can I Reinstall iBooks?
Copy the file from another system or a trusted person's machine

If you have a second machine with a comparable build of OS X installed on it, you can copy the file from it. Feel free to ask for the checksum of a file in chat to compare it to if you wish to make sure that the file is correct (not modified accidentally/purposefully).

Pacifist with OS X install media

If you've got an OS X install media and Pacifist, you can browse the install media and grab the file.



If you have Pacifist but no install media, it will prompt you to download the installer.