Dungeons & Dragons Fifth Edition has a different release schedule from previous D&D versions. New D&D 5e products come out less frequently in an attempt to keep options as well-made and balanced as possible. There is often one premade campaign a year and infrequent setting guides, and the game can go years between big player options books.
Source：https://www.cbr.com/dnd-5e-best-official-books/
