In the end the shelf looks great, but I nearly lost my sanity putting it together.  My advice is put the top part together first, flip it upside down, add the bottom legs on one at time, then the smaller crossbars, and then the X shaped part.  I’m using mine for an over the toilet shelf so at this point I lifted it up and slid it behind the toilet.  Then I took piece H and attached it at the bottom.  I tried other ways and nothing else worked.