It's on the surface and all over all around you. Mind as well take it in and enjoy it. Play with it. There isn't any escaping it really. I like the idea of taking what is around you, some of which has been spoon fed to you since you were an infant laying on the carpet in front of the TV -just a relentless onslaught of media images, memes, symbols, this American mass culture or popular culture- and regurgitating it. Throw it back up after having processed it a bit and make something interesting, maybe more interesting, out of it. Well, that is what's going on with some of this stuff. And some of it is coming from who knows where and some of it seems to be taken right off a shelf and repackaged.
Much of the art described as "lowbrow" and/or "pop surrealism" at this point has been widely visible and familiar to much of the public. So the surreal or weird becomes regular (as it often does). "Underground" in the title means not in museums or the top art galleries. I guess I don't care for the idea or metaphor of "underground". It doesn't make much sense to me, but anyway. I love some of this art, some of it not so much. If your unfamiliar and curious just check out an issue of "Juxtapoz" at Barnes and Noble or most book stores in the mall.
As far as this book goes, if you got 30 plus bucks to spend, it could make for a good coffee table book I suppose. It contains some essays worth reading if your interested in this art, including one by Robert Williams who is a central figure of the so-called lowbrow art scene. I don't agree with some of what these guys have to say, but they're interesting. There are nice selections from many of the most respected and influential artists of "pop surrealism" which, btw, is more or less refering to most of the art classified as "lowbrow", depending on who you ask.