Other DRM formats to consider are ereader and Mobipocket. Drm can be removed from ereader using ereader2html.py, and Mobipocket DRm can be removed using mobidedrm.py. Check
here for them. Since these are Python scripts you will also need Python. You can download it free from
here.
Please check your local laws to determine whether such DRM removal is legal where you live. And welcome to the forum.