tl;dr: steampunk planetary romance 5e conversion kit, heavy on the gear, lighter on the setting details.

This was a kickstarter I backed because a) I rode in on the 90s steampunk wave back in the day - Abney Park, the Difference Engine - all that jazz and b) I seriously contemplated getting myself a Weta Workshop raygun once. When Dr. Grordbordts Scientific Adventure Violence dropped on Kickstarter I backed it more on that nostalgia kick than I was expecting something mindblowing but now that I've gotten to reading it I've been pleasantly surprised.

Cover art by Max Chow

This is a 5e conversion book; following a similar course to what I have seen elsewhere of very much running with the system as it exists and applying mods through new conditions, tags and the like. The art is fun, the production values are very good indeed and there is lots of the original Dr. Grordbort material turning up in the pages which is neat. This is a toolkit to do this type of game in 5e, a mod-pack for familiar players, rather than an entry to the hobby for new folk. I would say you would need to be fairly familiar with basic 5e D&D to get the most out of this.

So what is all this stuff you get in the box?
Introduction - 12 pages of basic background
How to Play - 8 pages of the key tweaks to the 5e basic system
Character Creation - 46 pages with setting specific race, class, backgrounds etc.
Equipment - 106 pages of gear (also covering spells)
Grordbortian Mastermind Handbook - 24 pages of GM guidance
Interplanetary Bestiary - 48 pages of critters
Dramatis Personae - 41 pages of NPCs
Appendices, Index and Tables - 34 pages of tables

So what is in here chunk by chunk?

Introduction - 12 pages of basic background - the overall setting is Steampunk "British Empire to the Stars" - complete with the content warning on the front that this bakes in some topics and attitudes that will not be to everyones taste. It is supposed to be a satire of colonialism, imperialism and such - whether that is something that works at your table will be up to you and your players.

How to Play - 8 pages of the key tweaks to the 5e basic system - key different here is everything 'magical' gets converted to the sensible super-science of Gadgetronics - washed through a steampunk science system - and things need fuel. So your cleric is going to require a focus for their various spells that sits in a holster and also needs fuel. The interest in leaning into this is is definitely going to vary table to table - like encumbrance rules or magical components - but I guess it is supposed to be the balancing factor for having lots of super-science weapons at your easy disposal. For true challenge, make your ammo-cells explosive in case you get hit...

In Character Creation races get replaced with heritage to one of the planes in the system. This uses all the 5e structures of race, class, background, sub-classes and provides setting appropriate variants like Boffins (Wizard), Scapegraces (Rogues) and Evangelical Engineers (Clerics). You get some nice planet-conversions where voyaging to other planets gives you bonii and penalties depending on where you are from - changed gravity, atmospheres that may not suit you -

Equipment - a third of the book is gear porn - which is entirely expected given the heritage of this project as a world created to support the creation of awesome props. This is a setting built on the back of using your preposterous ray-gun to blast a hole clean through the charging venusian beastie coming right at you. Where things to get interesting is in the malfunction rating and the attachments you can add to your ray gun - each one useful but also increasing your malfunction risk by a notch. The malfunctions range from minor to catastrophic explosion so always a small risk to using these things and a good reason to continue to carry your trusty saber. There are techno-mounts, heavy vehicles and artillery, armour, scientific adventuring gear, airships, rocket fighters - everything needed to stage a good planetary romance.

Grordbortian Mastermind Handbook - this GN guidance starts with how Dr. Grordbort games are highly likely to descend into chaos, the tricky topics of a high imperial setting and how to reskin 5e concepts into this Scientific setting. Six pages of secrets and hooks for the planets and then the remaining half of the section is more gear with unique scientific adventuring gear.

Interplanetary Bestiary has martian tripods, venusian beasts, weird aliens from beyond the solar system and rebellious robots grouped by the planets where they are found. All good stuff.

Dramatis Personae - leaders of the various factions and a really interesting reversion to super-old-school world building where you got lists of the heroes of the realms. Normally I'd be looking for more on the worlds and factions and some texture to the setting but this is kick-the-door, ray-gun-the-baddies stuff so in fact you don't need setting complexity, you need your cast of villains and allies as provided here.

Appendices, Index and Tables - with malfunction tables for all possible classes of breaking thing - Artillery, Gadgetronics, Biofiddlery, Robotry, etc. Additional tables map all the 5e spells to their required Gedgetronics. We also get 'tuppenny equipment' which is a guide to creating the cheaper knock-off versions of all the gear in the book to bring them down to reach of a starter players - typically halving the range, doubling the weight and being just a touch less effective.

For some folk this is just what they want - all the possible rayguns and mad-science gadgetry to run their campaigns. For those seeking example adventures and a bit more on the 'how to run the game' side the free Quickstart adventure paths (five of them) fill in that gap. By the time you have worked through those with their mad science and satirical colonial shenanigans you ought to have a pretty good sense of what the game ought to be. Nice that these are freely available, shame that you have to go look them up separately - I think one of these being in the book would have made it all that touch more complete.

To wrap - this is a pretty straight 5e mod strongly rooted in character templates and gear. The world is fairly lightly sketched in, with a fair amount of additional worldbuilding available in art books from the pre-existing actual-physical-raygun range. Your best source material might well be old Dan Dare or Flash Gordon comics to get the attitudes right - War of the Worlds for some of the aesthetic, Stirling's Court of the Crimson Kings would be another.

This is a pretty player-facing book - character options and gear dominating - and a little light on how to run these types of games which are going to vary a fair bit from standard 5e due to ships, plentiful ranged weapons and heavy weaponry. You might want to combo this with adventures and game-running guidance from some other system - Stars Without Number? Esper Genesis? - to get a campaign rolling.