My current WIP is the first book of two (possibly three, if I start planning it and realize I have enough content to split it up). I already have the first book completely planned, chapter by chapter, ready to start writing as soon as my wisdom tooth extraction heals enough to get me off medicine. My question is, should I plan my second novel before I start writing the first? I know with J.K. Rowling, it took her forever to write the second Harry Potter book because she was planning all of the other books at the same time. And I have a book about writing a series that suggests doing it this way, so that you can drop in little clues in the preceding books to make them more connected. Plus, the book suggests it keeps me (the writer) from writing myself into a plot hole later in the series. Has anyone ever done it this way? Does it work, or is it a waste? Opinions? Thanks!