To this end, the book (and the nature of the contents in general) makes a good conversation piece. They also make a great example of how to distinguish the difference between "Comics" and my notion of "Visual Language", which is made clearest by teasing out just what parts of cognition these comics engage.
First, we should ask the question "Are abstract comics of this sort 'comics' at all?" I would have to say "YES" — simply because they call them so. However, they are not instances of visual language.
To repeat my theory... Visual language is a system of patterns (from people's heads) in that expresses concepts through the graphic modality using sequential images. So, visual language uses three interlocking cognitive systems:
1. Graphic modality
3. Sequential structure (i.e. grammar)
Like spoken or signed languages, this system is culturally relative, meaning that different cultures use different visual languages (for example, "standard" manga style versus "standard" superhero style dialects), and this system is used socioculturally in comics paired along with written languages.
Comics are written in visual language (± text) the same way that novels are written in English. Novels aren't English, and Comics aren't visual language. (This equation would essentially be McCloud's position, that comics "are" sequential images).
Given this, abstract comics most definitely are comics — because they call themselves comics, they are formatted like comics, they are made by people affiliated with comics, sold in comic stores, etc. They satisfy most all the sociocultural aspects that one would expect comics to fulfill.
However, they do not use visual language. They don't use representational depictions that reflect patterns in people's heads. They don't seem to have any sort of grammar of narrative structure. They don't depict any meanings at all. In other words, they use just one of visual language's structures from our cognitive system*:
1. Graphic modality
They are merely playing with the graphic modality in a sequential way that entirely lacks meaning (in the conceptual sense, not necessarily the "artsy" sense).
As a result, abstract comics make a great example of comics (and art) that lack visual language. This is the inverse of something like an airplane safety card, which is representational, but lies outside the sociocultural category of calling it "comics." I should say also, that this isn't a bad thing — it's quite fun, clever, and creative, and further goes to my point that these notions of "comics" and "visual language" are separate.
* Interestingly, the one cognitive structure they do use though, is visual language's navigational system for how to move through a page layout. In many ways this is an ancillary system to the primary VL system for expressing meanings in sequence, but it is curious that this seems to be one of the formal ways in which abstract comics get to call themselves "comics".
** I haven't analyzed the pieces in the book enough, but it is not inconceivable that graphic sequences with no meaning could still retain a narrative grammar. For example, Action Star substitution incorporated into a sequence with purely visual surrounding panels could lend to this result.