I kept waiting for a post script at the very end. Something like Langdon really brushing off all that he was told at the Washington monument and closing the door and
"little did he notice the faint etching beneath the spiral staircase that matched the (pick one - capstone, pyramid, ring). Little did he know how close he really stood to revealing the real secret treasure that laid hundreds of feet beneath the staircases last step, accessible only by (pressing / holding / turning the capstone / pyramid / ring) and removing the cover of the release mechanism that opened the access hatch to the real treasure. The Masonic treasure was still safe, that is until next time."
Good read, slow in the end, could of left off a few of the last chapters. Didn't see the antagonist's identity coming till it happened. Worth the $8 I paid but would not read it again.