When you read an exciting book to him, you are sharing the pleasure of reading. And don't follow up with quizzes and book reports -- you'll know if he's "getting it" by his reaction. Discuss the characters and the plot as if you are genuinely interested. Go to the library and get a lot of books on a number of different subjects. What are his interests? Soccer? Bugs? Rocks? Hockey? Mummies? There are so many wonderful books on every subject and at every reading level. Get basic books he can handle. Have him see that books are a source of pleasure and learning. Redirect your efforts to incorporate reading as a part of your life, not as a task to be completed only when you do "reading." After he's read about rocks, for instance, go to a hobby shop and buy some interesting rocks and minerals, then look them up in additional books. Or go to a museum and see the mineral displays. Same with snakes, turtles, or frogs.
Whatever method you were using to teach reading, try something different. Workbooks are often frustrating and boring. We used to write the word for all the objects in our house on small index cards, then pin them to the object. We'd walk around the house and the words became familiar. Later we took off the cards and made silly sentences with them. (The lamp sat on the cat's hat.)
Did I mention turn off the TV? Put away the Gameboys? Pack away the computer games? All of these are distractions and will interfere with learning.