This pdf is 21 pages long, 2/3 of a page front cover, 1 page SRD & editorial, leaving 19 1/3 pages of content, so let's check this out!
Multiclassing is a topic that is problematic at best - while on the one side it enables players to make characters that are more complex, on the other hand level-dipping can and has unbalanced more than one character out there. It is this problem recent Paizo-publications have addressed via Eldritch Heritage and Amateur Gunslinger ( the former from UM, the latter from UC) sought to address. It is here that SGG's feats of multiclassing start at (including a reprint of the feats, so all are compiled in one source): Essentially, this pdf provides you with feats that enable you to play e.g. fighters with a knack for some spells, arcanists with martial training etc. After an alphabetic list of the feats and extensive advice on how to use them and an optional rule on favored multiclassing, we're introduced to the feats.
Mechanically, these feats provide a slew of challenges for the designers: In order to keep the game-balance and keep them useful, many of the feats herein have the prerequisite of having no levels in a particular class. Once a character with such a feat takes a level in the prohibited class, the feat is changed towards a rogue talent, a certain feat or a similar benefit, making these feats valid long-time investments for PCs.
More than that, the guide also includes a slew of feat chains that expand e.g. upon the eldritch heritages of your character or your minor gunslinging talents. It should also be mentioned that not only "dipping"-feats are included in the deal - the Ajouga-feat (wizard/witch-summoner), for example lets you give up your familiar in favor of making your eidolon your familiar. There is a wide-variety of different options to scavenge signature abilities from other classes than your primary one and while I do enjoy the variety and balance of the feats, I can't help but feel that it will take some time of playtesting on the part of my group to find out whether/how especially the specialist path multiclass feats are balanced. While I don't have any concerns with regards to the dipping-feats or those that grant access to some of the unique abilities, those that grant access to higher level abilities still leave me with a slightly queasy feeling. Take the aberrant bloodline, for example...
That is not where the pdf stops, though: 5 feats for SGG-classes are part of the deal and provide great practical examples and advice for you to create your very own multiclassing feats.
Editing and formatting are very good and apart from one formatting error, I did not notice anything distracting. Layout adheres to SGG's 3-column standard and the pdf has no bookmarks, which is a pity, for it would make navigating the feats easier .The cover-artwork (probably depicting a character with the journeyman gunslinger feat) is awesome. Designing these feats must have been HARD. Seriously, balancing them, doing the math etc. is a daunting task and it did work out, as far as I'm concerned. While not all of the feats leave me with a comfortable feeling, that also stems from my own predisposition to keep classes and especially their signature abilities apart. Seeing that not all signature abilities can be taken via these feats and those that can be usually don't go into higher echelon territory somewhat alleviates my fear of them unhinging the game, though. As far as I can tell from my extensive lecture of this pdf, the feats herein provide an excellent and smart way of providing multiclass-options without going into the abhorred level-dipping territory, thus enabling the creation of more complex character backgrounds with rules-relevant consequences. One thing seeped into my mind while writing this - what happens when you combine the narrative-driven (and thankfully, relevant) traits from RiP's "101 Pirate & Privateer Traits" and combine them with feats like that? I really hope for more trait books with this new approach and potentially renegade feats of multiclassing to expand upon the concept, making finally an end of generic characters once and for all. That being said, it should come to no surprise that my final verdict will clock in high: At 4.5 stars due to the lack of bookmarks, rounded up to 5 for the purpose of this platform.
[5 of 5 Stars!]