Treating all audiobooks equally is a mistake. Audio books are a transformation function applied to physical books. Asking whether they count as books is asking the wrong question. The more important question is: "what am I trying to get out of reading this book? And will an audiobook help me to do this better?" The answer to this question will be unique to every person and every book. I read quite a few books for the…
They also help sometimes in getting the "musicality" of a work. I didn't know how musical Moby Dick was until I heard the audiobook narrated by Frank Muller. He transformed the whole thing. Like when one reads Shakespeare and only afterwards watches it live.
I tend to have audiobook+book combos for almost every book I love, since it's also a good way to continue "reading" even when ones eyes are tired...