Zoom in/out options for text in eBook

I am currently working on a Zoom in/out option for an Ebook. Students are the users. Also the maximum percentage of zoom is 300

Question in my mind is when the page is zoomed in which one of the below gives a best look and feel for a student or a best practise?

1. Page zoomed in - The text in the window is enlarged but page still fits to the window size
2. Page zoomed in - The text in the window is enlarged but the page needs to be scrolled right to read the rest of the line, and then scroll left to come to starting of the line and this goes on