He sounds fine. I have friends with boys who didn't say a full sentence until well after their 2nd birthdays. The docs don't worry about it until they're 3, so he's got some time! Also, kids the age of your son will often compartmentalize their learning -- if he's working on learning one skill, he won't focus on anything else until it's accomplished. And, like one mom said, it can happen overnight.
The bigger concern is whether he understands what you are saying to him. He should be able to respond to or at least understand simple commands or simple requests (come here, get down, do you want a drink?).
If you're concerned about his hearing, it's easy enough to hide from him and see if he responds to your voice or turns toward a sound, like turning the TV on (mine would come running down the hall for Baby Einstein or Elmo).
Rather than having an ECI specialist come to your house (they are, like many social support agencies, over worked and understaffed), you might simply take a look at their developmental chart. It's more realistic than what some pediatrician's say. For example, our Dr. handed me a list of things my child "should" do at 9 months -- it said they SHOULD be cruising furniture. Neither of mine cruised that young. The ECI charts include a wide range of "normal."
As far as ways to stimulate verbal development, the fact that you're concerned means you're probably already doing the right things. Just keep reading and talking to him. Narrate what you do throughout the day using repetition and a sing-song voice (Ok, Junior, we're going to the library, let's get in the car. Car, car, car. Time to go, go, go.). I noticed this making a difference with my son when we would wash hands. I would sing "wash, wash, wash" then hand him a towel and say "dry, dry, dry." It wasn't long before he was saying it too.
Songs in general are good ways for him to pick up vocabulary too. The Itsy-Bitsy Spider was the first song both of mine learned. They would wiggle their hands in the air singing "pie-duh, pie-duh."
Good luck!