Top Choices for Best eBook Companies?

I’ve been trying to find the  best ebook companies​  out there, but it’s overwhelming. Some offer huge libraries, others have better pricing, and a few claim superior formats or reading apps. Has anyone tried multiple services and noticed real differences in quality, selection, or device compatibility? Which platforms do you trust for reliability and variety? Are there lesser-known companies that are actually better than the popular names? Would love to hear your experiences!