I just want to add that the type of acid used to acidify the milk makes a great difference. Citric acid or acetic acid makes mozz taste rather bland. It's used commercially for direct vat acidification, but usually in combination with cultures, just as a way to speed up the process. The better directly acidified commercial cheeses use bulk lactic acid for acidification. It's still not as good as all cultured mozz, but it certainly has more aroma and flavor. Meaning for us home cheesemakers, we should stick with cultures if we want a good product.
I've never been able to get a good mozz using citric acid, and I've gone through a lot of gallons of milk trying. Fankhauser has two great recipes, as already mentioned. I think mozz is a cheese where you can't take shortcuts.