This is a very neat supplement if you want golem-like characters in your setting, and want to easily be able to implement it without too much fuss or hard work for the dm. It can be used for pcs or npcs; and the iron titan is a class you add to a character. The character, having at some point, having been turned into an iron titan from an original form.
There are plenty of special abilities and choices to be made. Good art so as to guide the reader in what type of iron titans can be created. Iron titans get a lot of resistances and invulnerabilities making them, after they level a bit, very suited to facing specific foes and existing in hostile environments. Woe to the party that is vulnerable to iron titans.
What I most liked though, was the "we can rebuild him" section. This covers converting a dead character over to an iron titan, and it also throw in the possibility of how a party could continue from a tpk (everyone comes back as an iron titan). In doing so, the character or party are rebuilt, taking the class levels of the iron titan. What also interests me would be the possibilities of multi-classing. Just a bit, to secure some very cool abilities to complement the MANY options for iron titans in this book.
There are also feats, including feats for huge titans. Yes, you can be huge, and that means you have huge guts.
[5 of 5 Stars!]