(Okay, so it could be argued that Skyfall and The California Iceberg aren't really SF novels, as they don't feature any technology more advanced than was current at the time Harry wrote the books. But if we start down that road, we'd have to put Make Room! Make Room! in the same category...)
In the first book, Tony Hawkin - an Apache Indian and manager of the book and print shop in Washington's National Gallery - is recruited as an art expert by the FBI to help them recover a stolen painting by Leonardo da Vinci. Hawkin has special attributes that explain his recruitment: he can speak Spanish, he knows about paintings, and there's no one else available.
It's this last attribute that clearly signifies that this book - and its sequel - are not standard spy novels... In some ways, these books are Harry Harrison at his best: witty, inventive, complex and lots of fun.
As Newgate Callendar, reviewer for the New York Times put it: "The hero ... is enjoying an Italian meal in a restaurant in Acapulco. Suddenly he finds his head lying on the table. 'They've ... they've drugged the spaghetti!' With this one nice stroke, Harrison puts into perspective the absurdity of so many spy stories."
Until the 1987 Tor reprints, the Tony Hawkin books were among the most difficult to find of Harry's novels... When yours truly was growing up, the local library listed a copy of Queen Victoria's Revenge. I saw it once, but it was in the Adult section of the library and my own library tickets were of the juvenile variety. I asked my Dad to take out the book for me, but he already has his allotment of books. And the next time I went - and forever after - the book was always "out". I've long suspected that someone liked the book so much that they never bothered to return it.