Not a valid price guide
A new edition of this mass market paperback gets printed every year. While some of the information at the front of the book will be helpful to new collectors, I believe the scarcity of color photographs and the placement of stamp images on pages far removed from the stamp descriptions make this a poor reference guide. My biggest problem with this "price guide" is that the values quoted for mint sheets and plate blocks are vastly over-stated. Any stamp dealer would be delighted to sell to you at Official Blackbook prices... In short, you have no hope of selling your collection at the values shown in this book. I strongly recommend that invest your money in one of the OTHER stamp catalogues on the market. The small incremental cost will be money well spent.