The $50 & Up Underground House Book

The $50 & Up Underground House Book teaches how to build the lowest cost, most sunshine-filled, best ventilated and driest underground houses of all. It teaches how to incorporate greenhouses, root cellars and fallout shelters into an underground home. It covers both hillside and flat land design, and explains how to solve drainage problems with dependable gravity rather then expensive, failure-prone building materials. It also details ways to pass or otherwise deal with the building codes.
The $50 & Up Underground House Book is the only book to explain in detail author Mike Oehler’s revolutionary Post/Shoring/Polyethylene building method, which cuts building materials to the absolute minimum.

Several Questions

 1) Why does this e-book with a 7th edition book cover have an ISBN: 0-442-27311-8  listed in Amazon/ISBNsearch.org for a 4th hard copy edition published December 1981?  There were no e-books in 1981. 

2) How does a book with a 4th ed /1981 ISBN number ....have 1992 and 1997 copyright dates on its copyright page?

3) Based on the 5 copyright dates listed inside this book - Copyright 1978, 1979, 1981, 1992, and 1997 - the 4th edition would be the year 1992 not the year 1981.

4)   The book cover says "7th ed” but there are only 5 copyright years so this book should stop at 5th edition . not 7th edition.