While there's certainly a lot of very well deserved hype for playing Chariots of Steel as a game in it's own right, this is far from just a hack for Flying Circus! I have been using its rules extensively in our conventional Flying Circus campaign, from the updated rules for weapons and personal attacks to it's very helpful systems for larger scale battles which I used to get through running an extraction of a downed pilot from a hostile airfield.
The book is packed with amazing art and details, bringing everything I loved from Forge World's old Imperial Armour books into the wonderful setting of Himmilgard. While it certainly makes me worry for the Author's health, the way each new weapon is lovingly rendered really immerses the reader into the world and its historical touchstones.
Personal favourites include the Panzerstampfer, which takes the very silly real world Saint-Chamond and transforms it into a beautiful mountaineering walker-tank. The move Tank Battle! is spectacular, exploring new concepts within the game's design space and building on its systems really well.