Green Ronin’s 2013 Mutants & Masterminds Deluxe Hero’s Handbook provides the rules for the third edition of their SHRPG (superhero roleplaying game).
The hardcover is 319 pages long, and unlike hardcover editions of some SHRPGs I could mention
Champions 4th edition, it appears sturdy and durable. As well, the art is generally of a professional level.
M&M is very, very distantly descended from the d20 system. It’s a cousin of Dungeons and Dragons, in the same way that a gazelle and an Arctops share a common ancestor.
(The gazelle is on the left)
In practice, M&M feels very different from D&D. Many of Green Ronin’s design choices will feel very familiar to old time Champions players: the point-based design system, the effects-based powers (where power descriptions are generic and it is up to players to define how the powers produce their effects), the logarithmic effects scale, the decision to have attacks more effective than defenses. I suspect this is less because GR is consciously following Champions’ example and more because Champions hit on nearly perfect solutions to problems universal to SHRPGs early on. I imagine that later SHRPG games will, given sufficient editions, converge on similar solutions.
The specifics of the game mechanics are very different. M&M puts more thought into encouraging game balance with rules about how points can be spent—for example, a character can be hard to hit or hard to hurt but not both—and the damage soaking system feels more like the World of Darkness’ than Champion’s more direct one point of defense reduces damage by one point.
M&M is aimed at players who like a lot of crunch in their system. While the quick character designer will let players produce characters quickly, understanding what the numbers you generated mean requires at least one person in the group who understands the game. Provided the group meets that condition, the game provides a flexible, reasonably well tested  set of rules suitable for four-colour adventures.
Mutants & Masterminds is available here.
The detailed descriptions you will probably skip past.
Roleplaying games tend to be a group effort. While Steve Kenson gets the lead credit for writing and design, other credits are as follows:
Adventure Design: Seth Johnson and Prof. Christopher McGlothlin, M. Ed.
Quickstart Character Generator: Leon Chang and Jon Leitheusser
Editing and Development: Jon Leitheusser
Additional Design: Ray Winninger
Proofreader: Glenn Hall
Art Direction: Hal Mangold and Pauline Benney
Graphic Design: Hal Mangold
Cover Art: Imaginary Friends Studio
Cartography: Phillip Lienau, Sean MacDonald, and Christopher West
Interior Art: Jeff Carlisle, Darren Calvert, Adam DeKraker, Talon Dunning, Tom Feister, Tariq Hassan, Steven Howard, Scott James, Georges Jeanty, Alex Johns, Leif Jones, Jonathan Kirtz, MK Ultra Studio, Octographics, Tony Parker, Ron Randall, Alex Sheikman, Kevin Stokes, Udon w/Chris Stevens, Dexter Vines
Publisher: Chris Pramas
And that’s not even getting into the playtest credits.
Table of Contents
The TOC is detailed, requiring two full pages. Despite this level of detail, there is also an index. Other games—Champions Now—could learn from this example. If you cannot find something in the TOC, odds are you will find it in the index.
Odds are people reading this manual are experienced gamers. In case they are not, this provides a very compact guide as to the nature of gaming in general and this book in particular.
This presents the core game mechanics—how scale works, how dice rolls work and so on—around which the rest of the game is built. Like many SHRPGs, M&M deals with the inherent range of ability between your Guy in a Mask and Trench Coat and your Flying Demigod with logarithmic scales: linear changes in many aspects produce exponential changes in outcome. An added benefit is that calculating outcomes can be very fast, if you know how to use log tables. For example, someone with 5 running (900 feet per round) who needs to cover 10 distance units (4 miles) simply subtracts the first from the second to find out how many time units it takes, and then consults the measurements table to see what that means in real world terms: 10 – 5 = 5 time units, which is 4 minutes. Or, you know, players can memorize what 0 means for mass, time, distance, and volume, how scaling works, and do a bit of division.
M&M uses the American units system and while there is a metric conversion table in the back of the book, it’s hilariously wrong.
This covers the essentials of character design.
M&M is a points-based system in which the player pays with character points to get the abilities they want. In theory, one could create a character from the ground up, limited only by the number of points available. In practice, characters tend to fall into a limited number of archetypes, for which pre-designed versions are provided. In addition, there is a quick design generator provided, which (using dice rolls) can produce a playable character in a few minutes.
Abilities are what other games call stats; intrinsic properties that define how well one accomplishes various tasks. There are eight basic abilities, most of which are familiar enough: strength, stamina, dexterity, agility, fighting, intellect, awareness, and presence. These not only define one’s basic ability with particular tasks, they’re also used to provide the starting values for defences (all of which can be improved with the expenditure of points).
Normal human values fall somewhere between -5 and 5. Player characters could, given sufficient points, hit 10 or more and as I said elsewhere, these scale on a logarithmic scale. A Strength 0 character can lift 50 pounds without straining. A Strength 10 character can lift 25 tons.
Skills have two components: one’s basic attribute-based aptitude (result of points spent on attributes) and one’s learned experience. Improving skills is extremely cheap. It’s possible for a normal person who has a lot of practice to be just as good at a particular task as someone who is cruising on inherent godlike attributes. In addition, a few tasks are limited to people with actual training. Anyone can try to sneak past a guard but an untrained person with impressive manual dexterity probably should not try to half-ass their way through open heart surgery.
Advantages are non-power benefits that provide characters with useful edges. They run the gamut from nifty combat maneuvers to grotesque levels of wealth.
M&M provides an impressive (but frustrating, given point limits) list of powers players can buy for their characters, all of which can be made more or less effective as the player decrees.
As many SHRPGs do, the game draws a distinction between the power—what it does in terms of game mechanics—and descriptors—how it does what it does. For example, two characters might have ranged attack 5. That will produce the same game effects for the most part. But one character might throw angry shrews at their enemies, while another might simply have laser vision. Anyone on the receiving end would be just as hurt by the hail of livid rodents as synchronized light emission. Unless, of course, the victim was able to absorb rodents or highly reflective, both of which are possibilities in M&M, in which case power descriptors matter.
Gadgets & gear
In answer to the Joker’s query about where Batman gets his marvelous toys, he buys them. This chapter outlines the process by which tools can be acquired by characters.
Action & adventure
This section covers combat: who goes first, consequences, effects of vacuum, radiation, contagious diseases, etc. Not to mention falling, an issue very important for superheroes who are all too fond of running along rooftops .
Players have it easy. They just have to come up with a single character. Game masters on the other hand have to roleplay the entire universe, from antagonists to background characters, from individual buildings to entire cities. This chapter provides guidelines, as well as some pre-generated examples.
1: I’ve played 1st and 2nd edition M&M, both of which had bugs. 2nd had one element I was sad to find absent from 3rd: easily abused rules governing how far people got thrown back when stuck by attacks. Hip-checking people into low Earth orbit was part of the fun!
2: Not limited to Western-style superheroes. Ninjas and wuxia martial artists are also fond of rooftop excursions.