The only time paper books become easier to use than paper books for me is when the book makes extensive use of really fine print in tables or has extremely long

The only time paper books become easier to use than paper books for me is when the book makes extensive use of really fine print in tables or has extremely long lines of monospace text such as badly written source code. The resolution of an iPad Mini 3 or iPad Air is sufficient to render all the technical books I use quite adequately. eInk devices do not have the resolution and screen size required for comfortable technical reading. With "Retina" displays on a decent form factor, magic happens. I use the iBooks reader almost exclusively since it has very good note-taking and place marking tools. The only thing iBooks can't handle is position sensitive layout, such as some "art" books which rely on specific typography and layout for conceptual flow. PDF can handle some of this, but if the format is not exactly the same as the iPad screen we're back into "I can tell I'm reading a PDF on an iPad" territory rather than "I'm reading a book". The Kindle is optimised for flowed text. Of course it is painful for technical books.