Talents were and are one of the most interesting parts of the d20 Modern approach to classes. By using classes based off the attributes, characters could be customized to a high degree through mixing the base classes as you developed. Talents, by contrast, rewarded you for sticking with a class long enough to develop special effects in that class. 22 Talent Trees is exactly what it sounds like. The art is minimal (which tickles this reviewer's cold dead heart), but the talents themselves are solid, most having to do with expanded specialization rather than new effects. (The few exceptions to this are often less balanced than the others.)
For those doing medical dramas with d20 Modern, there's also an expanded Treat Injury system for transplants. Much like the Surgery feat itself, I never quite saw the point of that level of detail in a system that modeled injury with hit points. No harm no foul, though, if you used Surgery in your game, you are likely to enjoy this small bolt-on.
With a sub-$3 price, there's no reason to pass up 22 Talent Trees if, like me, you still enjoy d20 Modern for its potential for character customization.
[3 of 5 Stars!]