Drop-off marketing is a pretty simple way to get book orders. Take along a couple of samples of your best sellers and visit office buildings in your area. Show the receptionists the books and make sure they become enthusiastic about them. Leave a sample or two along with your flyers/order forms. These can be left in a break room or shown around by the receptionist. Make sure your flyer states clearly that you will pick the orders and payment up from the receptionist on _______ (insert day) and that the completed books will be delivered on a certain day. If you drop them off on Monday, give them two or three days to get their orders together, pick up the orders and payment, then get the finished books back to them the next day or two if possible.
Use your creativity and come up with variations on the above idea. You could easily take an afternoon and visit quite a few offices in one geographical area. Your cost would just be your time and a few samples, and you might end up with a surprising amount of personalized book orders.