Another browser extension is GrabMyBooks, which lets you assemble an epub file from multiple web pages in desktop Chrome and I think FireFox. You could then put them in Dropbox, OneDrive etc. and open them with the ePub app of your choosing.
In the App Store, there are several apps that may do what you want on your iOS device, for example:
https://itunes.apple.com/us/app/eboo...890503038?mt=8