Sure fire by Jack Higgins with Justin Richards.
Resentful of having to go and live with their estranged father after the
death of their mother, fifteen-year-old twins, Rich and Jade, soon find
they have more complicated problems when their father is kidnapped and
their attempts to rescue him involve them in a dangerous international
plot to control the world's oil.
Cross my heart and hope to spy by Ally Carter.
Cammie Morgan is a CIA legacy and attends the premier school in the
world...for spies. The school hosts some mysterious guests with the code
name Blackthorne. When Cammie is blamed for a security breach that
threatens to expose the school's top secret status, she and her friends
face danger to clear Cammie's name and learn the truth about
For Freedom: the Story of a French Spy by Kimberly Brubaker Bradley.
Despite the horrors of World War II, a French teenager pursues her dream
of becoming an opera singer, which takes her to places where she gains
information about what the Nazis are doing--information that the French
Resistance needs. Based on a true story.
You may also enjoy these adventure stories:
Mortal Engines by Philip Reeve.
As this post-apocalypse science fiction begins, "the city of London was
chasing a small mining town across the dried-out bed of the old North
Sea." Cliffhanger chapter endings and heart-stopping action keep Tom and
Hester's story moving at breakneck speed. The sequel is Predator's Gold.
Although these books are not precisely spy/adventure stories, they have
lots of action and unexpected plot twists that keep you on the edge of
Tomorrow When the War Began by John Marsden.
The female narrator leads a group of teenagers who escaped capture by a
foreign army that has invaded their country (Australia). Ellie and her
friends (both boys and girls) plan several military counter-measures in
this novel and the sequels.
The Gadget by Paul Zindel.
In 1945, having joined his father at Los
Alamos, where he and other scientists are working on a secret project to
end World War II, thirteen-year-old Stephen becomes caught in a web of
secrecy and intrigue.