I think one aspect people take for granted is book design. And when I mention book design, I speak of it in general terms. I think when people hear about book design, they’re thinking of coffee table books or the book’s cover. Well, illustrations and book covers are part of a book’s design but it’s more than just that. It covers the book’s size, the book’s paper, whether it has a table of contents (please do, unless you’re a pamphlet) or page numbers (unless it’s a bleed, please add page numbers otherwise a table of contents doesn’t really help out much), etc. And it’s not just the book designer who’s involved in this process. I think the publisher and even the author have something to contribute. I mean it’s the publisher typically who dictates what the final dimensions of the book are. An author might be asked whether he has something to add to the foreword, the appendix, the index, or whatever (or whether they should be present in the first place).
Even if the book isn’t going to have lots of pictures (i.e. a novel), book design plays a huge role. Choosing a typography and its size has a big impact on its readability. Overly elaborate typography (i.e. one that looks like it’s handwritten or too ornate) might do well as titles but they simply won’t do as conventional text (because it takes too long for the reader to process them). Another factor is the size. Size 10 might be too small for a hardcover book but it might be just right for a paperback (that also shows you how we process material—it’s not necessarily about size in general but proportion).
The thing with book design is that it struggles with budget, especially when it comes to paperback books. There’s actually an optimum size for reading a text given set dimensions yet designers don’t always pick that method, whether it’s larger typography or wider margins. Because it’ll cost more to publish a book using that method and it drives the book’s price higher, something consumers aren’t necessarily willing to pay for. And in certain ways, those spending habits can be seen in the real world, such as people’s choice to buy hardcovers instead of paperbacks (because the former is larger) or their choice to wait for the paperback release of a book (because it’s cheaper).
In D&D, I see people complaining about the new Monster Manuals. The old design had two or three monsters cramped up in two pages and that leaves room for more monsters overall. Lately, the direction the publisher has been heading is that one monster gets two pages, giving enough space for authors to flesh out those monsters and on the side of the reader, to see them more clearly and navigate through them better. Unfortunately, you also end up with a product that has less monsters for the same number of pages. Both design practices have a following (and war over which is “best”) and it’s a perfect example of how book design is a constant tug of war. Do you want a book that gives you more bang for your buck or one that looks pretty? And even if you were the most utilitarian of people (like me), you’d still want a book to look pretty. Aesthetics doesn’t necessarily factor in but usability does. I mean if we want the most tightly-packed novel, they’d be printing it with a small type face, such as size 6 for example. But size 6, while barely readable, isn’t convenient for me to read. At that point, the text might as well have been in Chinese. And so how a book looks has a bearing for me, even if I could do without the book’s cover art. It's also the same reason why given the chance, people choose books over photocopies of the same manuscript.