You are looking at seven the Hardy boys books, including:

#1 The Tower Treasure by Franklin W.Dixson 1998

#2 The House on the Cliff by Franklin W.Dixson 1998

#10 What Happened at Midnight by Franklin W Dixon 1991

#15 The Sinister Signposts by Franklin W Dixon 1997

#17 The Secret Morning by Franklin W Dixon 1998

#18 The Twisted Claw by Franklin W Dixon 1999

#30 The Wailing Siren Mystery by Franklin W Dixon 1998

#37 The Ghost at Skeleton Rock by Franklin W Dixon 1998

Please note books one and two are in one hardback book.

Thank you for looking!