I use my iPad Pro with Google Books. It's not the reader with most features (this is sarcasm, it has zero features) but if you only want to read it's super easy

I use my iPad Pro with Google Books. It's not the reader with most features (this is sarcasm, it has zero features) but if you only want to read it's super easy to upload the pdf to Google Books and it remembers where you left off if you're using multiple devices.