So then what is in a book?
Well, if I take the road that a word is more akin to a sound than a quasi-abstract object, I would probably be inclined to make a distinction between an unwritten word and a written word. An unwritten word would then be a sound while a written word would then be a representation of a sound, much like the numeral three is a representation of the number three. So, a word would be either a sound or a representation of a sound.
Would we therefore (I'm curious) deny that a sound is immaterial because material is a necessary component to generate sound? See, to me, this is where things get sticky. Why must we be so quick to dismiss the notion that such things are immaterial on such a basis? We do disjustice to language when we narrow the scope of what constitutes immateriality. Suppose the material constituents of what we think is sound isn't actually sound but rather what gives rise to sound, much like the notion that a brain gives rise to a mind, where not the mind but rather the brain is what's made of matter. If a spoken word is the consequence of the material in action to make sound, language affords us the ability to delineate between the material word and that which is immaterial without making it sound mystic. It's apart of our language (not misunderstanding) to speak of things that are consequences of material-bearing events. In other words, the idea that certain material events create things to which we can acceptably be spoken of as immaterial is not being considered. The insatiable desire to deny this is seen in the brain mind distinction where people can't for a moment consider the notion that certain things often regarded as immaterial are not only a function of that which is material but actually a byproduct of language.
Don't hold me to all that. It needs some work.