Adamant Entertainment's Thrilling Tales has been a top-notch pulp game for many years, whether in its d20 Modern incarnation - as in this collection - or in its current Savage Worlds incarnation. By going directly to the source material - 1930s and 1940s pulp stories, Thrilling Tales has a unique, authentic feel that "neo-pulp" approaches like the Indiana Jones movies lack. It's not afraid to shy away from the weird - period pulps emphasized action and adventure over perfectly assembled plots or deep characters.
The Advanced Class Collection assembles 8 advanced classes from the Thrilling Tales line.
The Mystery Man is a masked crimefighter, who combines combat effectiveness and investigative prowess, the Air Ace is a stunt and combat pilot, the Paragon is a unique Doc-Savage-esque near-superhero, the Mesmerist is a powerful hypnotist, the Mad Scientist, Mastermind is just what it sounds like, the Noble Savage is a Tarzan-esque master of the wilderness, and the G-Man is an investigator who also has abilities related to government backup.
Although each of these are very fun and flavorful, there's a few things to note: first, game balance is not a goal of these advanced classes. The Paragon is just better than any other advanced class out there, which is as it should be - in Doc Savage stories, he really was better than most of his compatriots. The idea is that this would be the central character of your series, and the other characters would be support characters. It's not a problem exactly, but it's something to be aware of.
If there's a weakness to the collection, it's that there's not much attention to integrating the classes into your campaign. While each of them are flavorful and interesting, it is hard to decide exactly how to use them. Some attention to how the Air Ace would fit into a campaign would especially be nice, since plenty of times characters based around vehicles or transportation have a difficult time becoming part of the action outside that transportation. While the Mastermind is mentioned as being a villain, I think it could be interesting to be a Mastermind player character - some incarnations of the Shadow are best understood this way. Developing how these classes affect gameplay would be the best way to improve this product.
In general, if, like me, you use your advanced classes as a way to make d20 Modern campaigns distinct and flavorful - even if they're not perfectly balanced - this product is for you. You might even get some good ideas for character types for your Savage Worlds Thrilling Tales game if you don't have a lot of experience with pulp archetypes.