The other is about skin creams, lotions and ointments used for skin rashes.
This one is about pills, patches, shots, and intravenous medications given for pain relief.
Other than the subject matter of the ebook, there is no difference. Of course, they're not at all interchangeable. Images relevant for dermatology (a tube of skin cream) wouldn't apply for the pain medication ebook (pills, shots, etc.)