Physically Based Rendering Book

Edit: To be more constructive:

Physical reference books are often accessed in a non-linear fashion, and often not alone. But let's forget that second part and focus on non-linear.

How do people take a physical reference book and provide themselves with good non-linear access? Bookmarks, tabs, dog eared pages, margin notes producing cross-references if absent from the text proper. And they may even sometimes pull out all the bookmarks and tabs and start over to create an entirely different (for their use-case) reference text (by "hiding" irrelevant information). That's what needs to be recreated in an e-reader, not page flipping, to be useful for reference texts.

As a point of frustration I recently experienced, I was running a TTRPG game and had a PDF with bookmarks to various classes (the ones players were using) and spells (ones I was using) and combat mechanics (what I was running). I later used the same PDF as a player, and found that I had too many bookmarks that made it hard for me to find exactly what I wanted. If I just added more bookmarks relevant to me as a player (playing a class not in the game I was running) it would add extra info to the DM version of the reference, and all the DM bookmarks were largely useless to me as a player.

What I needed was a way to get two views of the same underlying text, with different sections emphasized or elided for my differing situations. Provide that in an ereader without having to make a copy of the PDF and manually mangle it (which I've done too) but rather just an overlay on the existing text and it'll provide a much better experience and start competing, realistically competing, with dead tree reference and technical books.

Of course, the inability to (without a large display or large number of displays) view multiple texts side-by-side is another problem. I don't want 10 e-readers (a guess at the largest number of texts I needed to view in parallel). I have my iPad, laptop, and a Kindle that I already sometimes use simultaneously rather than printing material off or buying physical books. It's painful to use things that way and a much harder to solve problem without insisting that people buy more and more hardware. Which becomes obsolete quickly, probably faster than most reference and technical books become obsolete.

2. You need something to base your opinion on though, preferably peer-reviewed scientific studies.

You read way too much into my comment.