The best ~Spy Books~ will not be up your street, yet.
But if you like spy books, when you are older and want a long read, where nothing is straight forward, and the spies spy on the spies (Quis custodiet ipsos custodes, who will guard the guardians themselves) then the John Le Carre Novels of George Smiley rule supreme.
Tinker, Tailor, Soldier Spy and Smiley's people are the two best, with ~The Honourable Schoolboy~ making up what are known as the Karla trilogy, but they are not fast paced, gadget filled killing baddies, they are very intellectual deep reads, but sublimely written and constructed.
If you want a fast paced good spy thriller, then ~The fourth protocol~ by Frederick Forsyth will be what you are looking for, in fact most of the Forsyth books are thrillers and spy novels.
But when your intelect takes over and you want a sublime read that you can re-read and find things you missed the first time, then re-read and find you were wrong both times, the too fat and old George Smiley rules.