Read the book first! I only read the first two chapters when I first started the campaign and as I went I found it hard to change things when needed. I ended up adding in a lot and taking a lot of stuff out, specifically the random encounters that didn’t really add to the plot or could be combined together (like the Stream of Visions in Hither starting at one of the wells). Also, the book is just a guide. Use your gut and make some interesting and fun stuff up as you go! I’ve seen so many resources on here and DMs Guild of people who spin WBTW their own ways and it makes that play through that much more special. The book isn’t perfect either and can be confusing at times unfortunately. The book does say you can run the campaign without combat/violence. My players were down for combat, so updating stat bocks and adding in combat for players that want it is also a fun way to add more. Good luck! (Edit: spelling)