Audio Books and Page Count?

So I'm getting near to finishing my first audio book, Shirley Jackson's The Haunting of Hill House. I finally found that I can play it straight from my web browser with headphones while cross stitching/crocheting/playing with my digital ponies and I'm quite enjoying it.


My question is this: I do a monthly round-up that includes page count for everything I read. While I am absolutely including my rating of the story in the average I do there, what do I do with something like this that doesn't use a word count? Do I not count it at all? Is it fair enough to find and average of the page count (or the lowest page count, or something like that) and use it in my averages? How do audio books work in this sort of thing?


Or, since I figure there probably aren't hard and fast rules on this, does anyone have any thoughts on what they think makes the most sense? Should I include separate averages on time spent on audio books and average time spent, etc? 


I have really no idea; I'm proud of myself for branching out a bit, but as I approach the end of the book and the time where I would normally be tallying up the page count, I find myself totally bamboozled. 




Edited to change it to Page count, which is what I meant in the first place and what I used throughout most of the post.