It's a solid little addition to an already excellent system; including not just some great new crunch and some fun planes, but several excellent story hooks and plot ideas. Also, rules for skiing, and as someone who loved skiing in my youth I'll always mark out a bit for that being added to a system.

If you have the Core Book for Flying Circus, Horrors of the Heights puts a maganifying glass a rule set that more or less hand waved till it becomes Plot Releveant: The Effects of Alitude on People and Flying Machines. On top of a focus and expanstion on atltiude based play, this also includes new and exepanded threats and rewards that hint to terrible new dangers and glorious forgotten tresure hidden in the the dizzying of heights of over 30,000 Ft. In grand Flying Circus fashion, this book is part Pulpy action adventure, part detailed simulationists rule sets but all friggin awesome!

This was a very good read. It doesn't has many new rules, tho the ones it has are very very significant. It mostly adds a ton of new ideas and lore to the world of Himmilgard. In this world where the sky and flying are so important it makes sense that the sky holds many unknowns and that are the source of myth and legend for the people that live here.

I'm particularly fond of Leaviathans and Flying Fortresses and their Fortress Guardians. I want to play a guardian!! Truly a great adition to the Flying Circus game

As an expansion, this doesn't have the sheer page count that the core book does, but it's really efficient. With three pages for altitude, temperature and extreme conditions, it builds a new environment to fly in that can be challenging to brave on its own, four pages for mountain terrain build a new type of land to fear and respect in equal measure and add a bit to regular ground combat, and so on. It punches above its weight, fitting tantalizing snippets of lore in new enemies and a whole variety of new challenges and adventures to take part in.

One thing I would appreciate is a few more planes that are well suited to the high altitudes, or worked out examples of existing planes modified. I'm fine living in the plane builder, but I know other players might prefer not to get into it or play with planes they know have gotten balancing attention.