Having a look at my method of writing gamebooks compared to other ways.
Some have A Strong Narrative
I think many gamebooks are written with a particular storyline / arc in mind. Seeking to unravel/escape a series of murders in a Victorian hospital (Nighshift), seeking two parts of a dwarven hammer from a fantasy forest (Forest of Doom), attempting to save the world from an ice age possibly caused by godlike AI (Heart of Ice), Finding out what tragedy happened in a haunted house 10 years ago (House on Sentinel Hill).
Typically you'll have a storyline and some possible endings (all but 1 being Bad Endings in the case of Fighting Fantasy), work out different paths to different endings, branching and merging these paths as they go. There might be a couple of points where all of these nodes meet.
They'll also be varied approaches to playtesting, feedback, reworking and repeating this.
There are some old blog posts on gamebook structure with Classifying and Rating Linearity by Jake Care, Beyond Branching by Emily Short and How Many Endings does a Gamebook Need by Dave Morris.
Open-World Writing
Open-World gamebooks are a little different. Granted that there's a limited pool of open-world series and gamebooks out there, (5ish series and a few individual gamebooks) but there are common elements nonetheless.
Because you can wander from place to place (and back again) in an open world gamebook, the design is different. It's centred more about locations. Much of the design and writing will be getting between locations, setting up parts of quests between locations and the thankless task of testing out routes, codewords, quests and the permutations.
This applies to series of open-world gamebooks (Fabled Lands, Steam Highwayman) and individual gamebooks with an open-world structure (Isle of Torment, Lost in the City).
Some open-world gamebook series will have a stronger storyline, such as the battles of Legendary Kingdoms (and focus on a different character for each) or the 12 heroic trials (3 for books) for VulcanVerse. Here you will need to gate off certain parts of the book, until the characters are ready for it / have fulfilled the bits necessary to unlock it.
My Own Writing (so Far)
I'm an aspiring gamebook author, so I'm still finding a favoured way of writing (open-world) gamebooks.
I'm very loose in my opening idea, with a vague idea of what it's about and the feel, with a very loose setting. "Lost in a misty fantasy forest". "on an island of sorcerers that was moved by magic"
To start with I'll make some simple locations in the realm (A lighthouse, an inn in the trees, the Chasm of Dreams, a bridge over a river, a talking tree by a ruin) and then connect them together so you can traverse the world. I'll add in a few encounters, make the basic rules and add a few NPCs.
Then I'll print it out and try playing it as a physical book.
At the start it will be a pretty rubbish gamebook. Sparse text, locations with none or one way to interact, mechanics with little support, exits that go to blank passages.
Then I'll note things I like, remove things that don't work, add detail to locations, more mechanics, expand on NPCs, add more encounters, rework areas.
Print out, playtest, make notes, revise, expand, improve.
Repeat and iterate.
Slowly the ideas will combine into a concrete plot idea, themes will emerge and strengthen.
Then it's time to take it to others, for more playtests and other feedback.
Take notes from playtests, revise, delete, improve, polish, rework, finetune.
Repeat and iterate.
I've taken one gamebook to the point I'd be almost happy printing it. But it's part of a series I'm not ready to write the next one of yet.
The current gamebook I'm working on (and hoping to be first one to publish) I'm at the Themes and central plot starting to emerge. Just printed it out and playing through it again...
Finishing Up
How do you write your gamebooks? (Comments can't be left at moment but we've got a gamebooks Discord!)
