I'm currently in the process of writing a book, and I'm using mostly OFL fonts in it, but I also find some Apache licensed fonts very attractive and would like to use them.
The condition for using Apache licensed fonts in code is to attribute it in the code but in my case, should I attribute them in my e-book and print book (which will be a commercial use product)? Also if yes then how can I make it so that the license becomes less disruptive to the book reading experience itself?
First, I strongly discourage you from trying to specify a font for your ebook. Most people can't figure out how to do that, but you sound like you might know how to code it into an epub document or something. Please don't. Part of a satisfying ebook experience, for the reader, is being able to change the typeface and font size to suit them, and have the text re-flow smoothly and naturally. If you've somehow locked it into one typeface, that creates a potential irritant for your readers.
Second, the print & PDF version of any book that uses interesting custom typefaces will mention those typefaces on the publication page (the backside or "verso" of the full title page), or sometimes on the colophon page, but most POD books don't include that in their front matter anymore, and most print books are POD.
A typeface attribution will sometimes appear at the bottom of a blank page at the back of a print book too, usually the verso of the first blank page on the right-hand side of the book when it's open (the "recto" page of a 2-page spread).
So yes, feel free to list your typefaces and cite Apache. In an actual print book, you won't need to reproduce the license agreement itself; for a PDF, you will need to do so, but it won't interfere with the readability of your book. You can do it in small print on the publication page if it fits (it probably will, unless you're cramming a ton of information onto your pub page). Otherwise, put the attribution and the whole license agreement after the first blank page at the end of your PDF (don't worry about verso or recto in a PDF).
And if you care about how your text looks but aren't familiar with the complexities of typography, this might be helpful, or at least interesting. Here's another fun overview of typeface and how to choose wisely.
I hope this helps!
