Is there a way to tell, when a book is discribed simply as paperback, whether it is a regular 8 inches by 3 inches or if it's the bigger bible sized version? 

If you click on the title, then on "more options" --> "edit book data" you can see if the dimensions are there.  Often they are correct, but not always.  And the sender has no obligation to be sure the dimensions are correct when posting the book.  (The title, author, ISBN, and "book type" have to match the listing, along with large print, if that is mentioned.)  And checking Amazon is a great idea.

I usually just check the original cost on Amazon. That tells me if it's Mass Market size, Tall Mass Market size, or Trade size.

The size data on Amazon can be pretty unreliable -- I've seen folks that just put "8" in every box -- 8" wide, 8" tall, 8" thick, weighs 8 pounds, etc.

If you prefer one size or the other, you need a Requestor Condition to ensure it.

I do prefer the regular sized paperbacks, but I don't really care that much.  I just wondered if there was an easy way to tell for curiosity's sake.  Thanks, folks.