In this picture it looks like the front cover was completely detached from the rest of the book and then glued back on. That's why the cover won't open all the way. A thin line of glue was run down the edge to re-attach it.
Usually re-gluing refers to gluing the complete wrap (front cover, spine, back cover) back to the interior of the book. In that case, the glue is applied to the inside of the spine.
Your case is much more severe. The cover had been torn from the spine, and then reattached. In my opinion this is not a VG at all, but a restored Fair to Good minus.