My high school was mainly textbooks, then things were more digital in college. Normally I'm against fancy new tech, but this felt like an improvement in hindsight. I was never missing the book I needed, there's cmd+f and page skip, I can annotate without ruining it...
The real problem seems to be licensing. Lots of books are physical-only, and the digital versions are those annoying "epub" files instead of PDFs.
Yes and no.
PDF's work well for a sufficiently large e-book reader. Full-sized isn't essential, though I find the 13.3" display I use is quite pleasant to read --- roughly equivalent to a large iMac Retina display for reading ease (less overall real estate, but more comfortable to hold in one's hands, and of course, read under bright light / direct sunlight), and vastly superior to a typical smartphone.
Smaller displays of 8--10" should work in most cases and are far more affordable. The exceptions are typically scans from print, especially of small-font and tightly-rendered journal articles, or works with extensive graphics and diagrams. Those with young eyes can probably manage better than the olds.
ePub fits any sized display, but there are times when fixed layout truly is preferable for reading, context, understanding, and juxtaposition of text and graphics, etc. With a fixed layout and a competent layout engine or editor this can be optimised. With a flexible layout* (HTML, ePub, etc.) the dynamic element pretty much always leads to compromises or gaffes in layout and positioning.
Fixed-layout also means that spatial memory of where within a document, chapter, and/or page specific elements / contents are. Dynamic layout greatly reduces the ability of those who have strong spatial memory of written materials.
My understanding is that MS Word's layout (as with some other word-processing software) was strongly dependent on the print drivers installed. So there still was some variability in output.
I tend to prefer LaTeX or a similar doc-prep system myself for authoring.
Aren't PDFs a relic of the past, when you wanted to print digital documents on paper?
Epubs can be reflowed to fit any screen. If done properly at least. For PDFs you basically need an A4/letter screen to read them comfortably.