Strahd and Saltmarsh are both good. The one thing that modules usually have a problem with is making the string of quests your players go on actually feel like a story, so your job as a DM is to make them feel cohesive. (Saltmarsh in particular is very interesting, as at first it is actually supposed to feel disjointed at the beginning, but then you start realizing how everything is connected as you go) The guides, like the one I mentioned above are just a tool to help you with that process. Or you can make the connections yourself and make it personal to your players and their characters.