While the idea of "reversing" or otherwise finding new uses for established skills in a rules system is an interesting idea, the examples here seem to run counter-intuitive to the common understanding of core rule mechanics and the ideals of roleplay in general.

"Reversing" an Athletics or Strength check to try to handle something with care is a bit of a stretch. Dexterity is generally understood to include fine motor control, so most players and GMs are going to use (and expect fellow players to use) those sorts of checks. A nimble thief with practiced lockpicking skills is going to be better at handling situations requiring a light touch--as would a master archer who has grown accustomed to minute adjustments of their body to improve their long-range accuracy. The beefy barbarian probably wouldn't be the one to turn to in that situation.

I don't think it's wise from a gameplay standpoint to use a skill to do something wholly outside its written purview, or to do something that is generally governed by an opposing skill already. Allowing a Bluff check to reveal if someone else is lying overpowers the skill, and removes the importance of skills like Insight that are already used to sniff out falsehoods.

On the other hand, "reversing" an Acrobatics check to appear clumsy sounds totally feasible! Normally this sort of endeavor would be the domain of Deception and Charisma, but you could easily make the argument that getting good at a skill allows you to better understand what makes someone bad at it--and then to mimic those behaviors. But there's a difference between being bad at something, and using a skill to accomplish an opposite or unrelated task.

I also feel that most groups should carefully consider whether they should allow dice to control things like character motivations or mental states. Using Lore to actively forget something you learned? Rolling a Persuasion check to see if you hold onto a personal bias or not? Rolling Intimidate to see if you're afraid? If you relegate these things to chance, you start to cross a line where you are not in control of your character's heart/soul: the dice are.

Ultimately, this short document has some neat ideas and new takes on skills that GMs and players could potentially mine, but I recommend readers give thought as to which of these will actively improve your game and allow for creative opportunities, and which will carry a risk of disrupting play, creating balance issues, or sowing confusion on how these rolls should work.

Zeitgeist is hands-down the best adventure path I've ever seen, and it all starts with this Player's Guide. The book is an indispensible aide to creating characters built for and molded by the continent of Lanjyr, and is brimming full of little tidbits to both inform and immerse you in the steampunky-flavored setting.

VISUAL The art for this guide is very attractive, and instantly sets the mood by giving you concrete visualizations for the fashion and culture of the adventure path's setting. Even the page borders and font style/color choices seem very purposeful here, giving the campaign its own feel while not being overly distracting or difficult to read. Stat blocks, player powers, and feats are all laid out in a manner that readers of the 4E core rulebooks will instantly recognize, making it easy to identify information at a glance.

The organization of the book itself is also very intuitive and useful. The introductory chapter brings setting-vital information to the reader's attention, laying out the differences between a game set in the world of Zeitgeist versus a normal game of 4e Dungeons and Dragons. Somehow, in just two and a half pages, you'll be almost completely up to speed on everything important there is to know about the game world, including a brief account of important historical events, the nature and culture of the different races, names of some key NPCs, and how to use the remainder of the book to your best advantage. There's even a pronunciation guide to many of the setting's invented words, which I wish were an industry standard for these kinds of books!

FLUFF Beyond the need-to-know background set down in the Guide's introduction, there are three whole chapters devoted to fleshing out the world around the PCs. In the campaign, the PCs begin as constables--agents of the King of their home nation with authority above normal law enforcement. This ends up being a far cry from the typical identity of freelance 'adventurers' that most players are familiar with, but the book goes above and beyond in its delivery of story and world-building to acclimate them to their new role. Particular attention is wisely given to the topic of the agency the PCs find themselves members of, as well as their main city of operation.

In the chapter outlining the various nations of Lanjyr, mixed into the nitty-gritty details of rulers, population diversity, and geography are stories of heroics from ages gone by. This added lore makes it easier to digest the overall 'themes' of each country, and the 13 adventures of the campaign often reference or breathe new life into these stories, rewarding players who take the time to learn more about their world, while not punishing those who don't.

CRUNCH The biggest draw of Zeitgeist (beyond its wonderfully-crafted and cinematic adventures) has to be the "character themes" from this book. Using an often-overlooked element of 4e D&D character creation, Zeitgeist instantly gives your character a place in the world. Any character can qualify for any of the nine themes, which not only gift you a nifty power or two, but also subtly influence certain parts of the story and gives each character a place in the spotlight during each adventure. For example, choosing the Skyseer theme gives a character limited divination abilities, but also grants them a pre-scripted vision once per adventure about the dangers and opportunities that their party will face in the near future. Choosing Technologist will give a character a robotic companion, and the ability to automatically succeed on Intelligence checks to operate complex new technology they may come across. The Paragon Paths are extensions of each theme, and while they don't tie into the story as much, that's probably for the best. All of them are setting-appropriate and have cool abilities, but they don't pigeon-hole your character's development; you can feel free to use any of the oodles of alternatives from other WotC supplements.

The campaign also uses a new Prestige mechanic to track the party's fame (or infamy) among several of Lanjyr's most powerful organizations. Events in each adventure can enhance or worsen your party's reputation among these groups, which open up new opportunities or trigger optional scenes in the story. One of the most common applications of Prestige is the ability to call in favors: the more Prestige you have with a group, the greater the service you can request. It's a neat addition that gives the DM an easy way to track how the party is viewed by NPCs, and how to determine what resources the party can call upon above and beyond their own wealth and equipment. Also present are rules on how to handle the PCs' government stipends--since they're not adventurers, they can't just loot everyone they come across!

Given the level of technology in the campaign, there are also stats for firearms and other modern trinkets. To function more fully with the (now defunct) 4e online Character Builder, the firearms themselves have similar statistics to crossbows, though they have enough of a distinctness that they're not a simple reskin. Tons of enemies from the campaign use these weapons and (mostly) abide by the same rules of their use that the players have to follow, making for a strong and consistent theme of modernized warfare, even intermingled with magical attacks. Optional rules also exist for phenomena like gunsmoke, misfires, or improving the overall lethality of guns (thus slanting warriors away from the use of bows or swords).

Finally, the appendices in the back contain collections of reference material:

• Stats for soldiers or police officers that may aide the party at various points during the campaign, allowing for players to use them much like summoned monsters.
• Stats for ships and rules for Naval Combat
• Sample skill challenge formats for tailing or interrogating suspects, a HUGE help as these will happen time and again during the campaign.

DOWNSIDES/CRITICISMS The book isn't perfect (minor typos exist, of course), but nothing is so problematic that it detracts from the overall enjoyment or utility of this Guide. If anything, the greatest flaws are not in the Guide itself, but rather missed opportunities in the campaign's adventures that fail to take full advantage of everything that the Guide provides. Yerasol Veterans don't have as much time in the limelight as the other eight character themes, for example, and more story events could have been influenced by the party's Prestige levels, but both of those elements remain as worthy tools for DMs and players in and of their own right.

If I had to identify the greatest flaw in the Guide, it's that it becomes far too easy for players to mitigate or nullify the longer reload times of guns as related to crossbows. If you're a DM, consider making it impossible to reload a firearm without spending at least a minor action.

TL;DR This book is awesome, and a great way to get hyped for the Zeitgeist adventure path, even if you currently know nothing about it. Even if you don't plan on playing Zeitgeist, the Characters section is a great resource for building steampunky characters in 4e D&D.