The latest incarnation of Mutants and Masterminds is an evolution of the system, building on previous successes. If you like superheroes and variants of the D20 system, this is almost certainly the game for you. While the changes from the previous edition (and the core OGL) are noticeable, if you have played M&M before, you will have no problem picking it up. I have no complaints and think it is the best version of the game so far.
Mutants and Masterminds (3rd Edition): Heroes Handbook is a 233-page PDF (230-pages if you remove the cover and OGL) with writing and design by Steve Kenson and published by Green Ronin Publishing.
The layout is taken directly from the print version with a 2-column layout. The (many) tables are clear and interior is packed with impressive full color art. It is a great looking book, no doubt about it. The table of contents is very complete and there is an index as well, so finding what you are looking for should be easy.
3rd edition builds on the lessons of the previous versions of Mutants and Masterminds, combining flexibility and simplicity. Using the OGL as its basis for the rules, anyone who has played a D20 system game will have a basic understanding of the system though several parts of the game have been renamed from the base OGL (eight statistics rather than six, advantages rather than feats) and it uses a damage save mechanic.
The character creation system is point based and divided into power levels that provide a cap on, well, how powerful characters can be. This cap is applied to offense and defense, balancing off ability to hit with ability to inflict damage and ability to avoid attack with the ability to resist damage. The system is designed to minimize the danger of characters being maximized for combat effectiveness alone.
To help get players into the system there is an extensive chapter on character creation that talks about motivation, origin and other important things for the superheroic genre. Additionally, fifteen prebuilt archetypes (from crime fighter to martial artist, energy controller to mimic) are included as examples as what can be built or to just take and run with. Two example characters (The Rook - crime fighter and The Princess - powerhouse) are uses to show how character creation works.
Much of the book (about 60 pages or nearly 90 if you include gadgets and gear as well) is devoted to Powers, which are often the core of being a superhero, and ways to modify them. The power system is very flexible allowing a great deal of flexibility and customization in design of powers. It does not allow the same level of fine-graining as, say, Champions does but it is enough to build most characters and their powers.
The rules system is complete and clearly explained, though it might be a challenge to pick up for someone entirely new to roleplaying games. The Gamesmastering section is short but direct providing some good advice and ideas. Unfortunately while there are statistics for variety of basic NPCs (thugs, agents, animals) there are no sample villains or introductory scenario, both of which would be useful for new gamers.
Disclosure: As a featured reviewer for RPGNow/DriveThroughRPG, I received my copy of this product for free from the publisher for the purpose of this review.