(This review contains indirect Frostmaiden spoilers. Players beware.)
This is a truly phenomenal product. If you plan to run Rime of the Frostmaiden as a campaign, rather than a resource to pick apart for other uses, this is absolutely essential.
I picked up RotF last month and fell in love with its tone, overlapping stories, and balance of pulpy adventure with chilling horror. But there are structural issues at every level - plots that don't quite add up, exposition dumps, and a dramatic end to the first act which simply doesn't work using the material as written - turning a momentous decision into a foregone conclusion.
The material in this product helps at every point. At no point do the authors step over the line in telling you how to run your game. Rather, they save you time and offer you options to run the campaign your way.
It's helpful on every level. The most valuable content for me is structural: advice to help turn some exposition dumps into player-driven mysteries, to turn a forgettable opening quest into a hook to lure the players through the first sessions, and more. But even if you plan to run a pure sandbox, or put the group on a fast-paced cinematic railroad, the little details help. Encounter scaling. Alternative random encounters. Battlemaps for side-quests that were overlooked, including in digital versions such as that offered by Roll20.
I just can't recommend it enough. Using the material here saved me weeks of effort, allowing me to spend December putting my own stamp on the game rather than troubleshooting inconsistent travel times or piecing together likely player trajectories through the material. With its help I just ran a very successful first session which was greatly elevated by the content contained herein - including art, original NPCs, and structural guidance.
If you've spent £30 on the excellent but slightly flawed Rime of the Frostmaiden book, you owe it to yourself to go the extra £11 for this product.