There really is no opening with the most "book moves" in chess. Depends on your definition of "book moves" Also depends on your definition of "opening" The queens gambit certainly has many book moves.
Even the Ponziani has book moves in one variation of more than 30 for each side.
"book moves" can change every day.
The World Record in a sport discipline also can change every day.
Book moves = identical moves in at least 2 grandmaster games.
Opening = initial part of the game until it deviates from a known predecessor game
I did the king's pawn opening and got 9 book moves
The Ruy López Opening: Marshall, Main line, Spassky Variation has the highest number of book moves, 36 moves.May 23, 2022(Copied from Google)
my username...
Sicilian Defense: Open, Najdorf, Poisoned Pawn Variation Accepted, 10.f5 Nc6 11.fxe6 fxe6 12.Nxc6 bxc6 13.Be2
This has 25 book moves
okay
comment deleted by mod
Don't say something about another topic
I think you can get the most book moves by playing the Ruoy Lopez
nice
https://www.chess.com/openings/Ruy-Lopez-Opening-Marshall-Attack-Modern-Main-Line-Spassky-Variation
this one has the most book moves
Chess.com guves the sicillian defense nafdorf variation english attack 19 book moves for white and 18 for black 
Hey I know the opening with the most book moves in chess 21 book moves white 20 book moves black though black always plays the same move after the last book move so it should 21 book moves black and white too its
and that's the longest opening in the game don't think there's any free pawns this is a grandmaster opening and actually only 4 of the 1800 are a loud to play this
the reason nfd7 isn't book is because that's a middlegame move if it where opening it would be book
though if black position it can take and of the hanged pawns however black gets a terrible position
I figured an infinite opening method though they classify as good moves in review if you shuffle the knights around in the opening then back into the starting position according to international Chess rules if any book moves are played after will technically make them classified as a book move so if you shuffle the knight around infinitley then put them in there staring squares without making threefold repetition than you play that 21 book move long opening you get the longest ever opening to exist on Chess.com and if you use FIDE rules also most ever book moves boom over 100 each player
Queen's Gambit Declined: Orthodox, Capablanca System, 10.Bxe7 Qxe7 11.O-O Nxc3 12.Rxc3 e5 13.dxe5 Nxe5 14.Nxe5 Qxe5 15.f4 15 book moves for white 14 for black. Ruy López Opening: Marshall Attack, Modern, Main Line, Spassky Variation 18 book moves each