I have no idea why you would use a pen to turn pages???
But I agree with /u/thequantumcog that KOreader is very good. Except IDK if it has any cloud facilities, as I don’t use cloud much myself.
After I found KOreader I read ALL my books on my phone. To switch pages I just tape left or right side, but it can also use volume.
The setting to open at the page you were reading last is a bit hard to find IMO, you should probably be prepared to use a moment to learn the interface. But then it works very well with many nice features IMO.