Hi Joseph, The Waterdeep: Dragon Heist module on Roll20 contains everything the book also contains and are converted for use in a VTT. Maps set-up with dynamic lighting, tokens with stats, how to run the entire adventure for the DM, etc. You don't need to buy the Players Handbook, Volo's, or any other core book. The module has everything you need to run that adventure. If you want to expand on the adventure, like adding a few new encounters with monsters not used in the module itself you would have to either make them yourself (which is not hard to do but takes time) or buy Volo's or the Monster Manual. Also, while all the maps are set-up for dynamic lighting, only plus or pro subscribers can actually use it. I highly recommend getting at least a plus subscription but it's definitely not required to play, you can also manually reveal the map for your players. I hope this answers your questions and if you have any more let me know!
