Once upon a time, ads in books were extremely common. However, writers hated this, and many of them forcefully opposed the practice during contract negotiations.
One publishing house made the mistake of violating a contract provision against ads by putting a cigarette ad in one of Harlan Ellison's books. Harlan responded in his own inimitable way, as described in the "DID HARLAN REALLY MAIL A DEAD GOPHER TO AN EDITOR?" section of http://harlanellison.com/text/newsfaq.txt .
One publishing house made the mistake of violating a contract provision against ads by putting a cigarette ad in one of Harlan Ellison's books. Harlan responded in his own inimitable way, as described in the "DID HARLAN REALLY MAIL A DEAD GOPHER TO AN EDITOR?" section of http://harlanellison.com/text/newsfaq.txt .