I don't really like most cape books, as they tend to err towards sexist portrayals and recycled ideas. Which isn't to say good examples of that genre don't exist, of course.
One of the first modern comics to play with 'realistic' superheroes — i.e. what would happen to a world and its politics if individuals with Superman-level abilities got it into their heads to try to improve things. The first two volumes collecting the Warren Ellis stories (Relentless and Under New Management) are excellent, as are the five StormWatch volumes that precede them. Unfortunately, the quality of non-Ellis Authority material ranges from okay to abysmal, although I do have a soft spot for Millar's Jenny Sparks: The Secret History of the Authority.
Hopefully this will get a reprint as the first volume is particularly hard to get at the moment. In a sort of sequel to Paul Cornell's Wisdom miniseries, the UK's answer to Captain America teams up with a range of other niche characters for some good old-fashioned storytelling romps. The third and sadly concluding volume in the series, Vampire State is also the best and ensures it goes out on a high.
Characters from fairytales, rhymes and similar transplanted to a more-or-less modern setting with plenty of fantastical elements retained. As with many series, the first few books work as standalone material before pressing ahead with an overarching plot. The first volume is a murder mystery introducing characters, then book two, Animal Farm, adds a loving dose of farce to proceedings.
Great concept: how does the city of Gotham handle its resident super-villains when Batman can't be everywhere? The focus is squarely on GCPD's Special Crimes Unit with rare appearances by the bat.
Tommy Monaghan is a superpowered hitman who deals in taking care of superpowered villains. This doesn't make him very popular with more respectable vigilantes such as Batman, and the storytelling bounces between humour and pathos. Sometimes a bit too much so, and the lead characters were never destined to get a happy ending, but the first few volumes are top notch storytelling. And it took a while, but kudos for DC for eventually getting around to reprinting the run.
Alan Moore draws from centuries of literature for characters and the basis of this series, with endless references for literary buffs to spot. Volumes one and two also work extremely well as action-adventure storytelling, bringing together a team of special operatives (Mina Harker, Alan Quartermain, Captain Nemo, et al) to protect the British Empire. Basically not connected with the film of the same name, and a thousand times more entertaining.
Warren Ellis takes his turn to mine previous decades of storytelling, mixing superpowered archaeologists with everything from kung-fu films to Sherlock Holmes and Doc Savage. What unfolds is a mystery that pits Elijah Snow and his team against another group of explorers who've set out to monopolise the power strange alien artifacts bring for their own benefit. For added interest, often stunning artwork is matched to the area of popular culture referenced by each issue.
I found the strongest bits of this series by Garth Ennis were the opening and concluding chapters, but the rest is worth at least one read too. The plot revolves around a disillusioned preacher, Jesse Custer, given the ability to command others with divine authority. There are also vampires, an extremely high body count, and quite a lot of scatalogical humour. Not for the easily offended.
Hunter S. Thompson in the future, as ghostwritten by Warren Ellis. Essentially this is an framework for the author to muse on journalism, writing, politics, treasuring history and various other topics. Very irreverent and not suitable for kids, but you'd already guessed that, hadn't you? The first few volumes are relatively standalone, after which more focus is given to an ongoing storyline. Highly quotable.
The series that made Neil Gaiman. The first volume isn't necessarily the best starting point, but it's as good a place as any — a man tries to capture Death but gets her brother Dream instead. The following series dwells on history, classics, Shakespeare, and the nature of story. Best read as a teenager, but that isn't to sound dismissive — simply to say that it's likely to come as more of a revelation at that age.
Probably best summed up by the title of the third collection, Change or Die. The kind of comics writing that only flourishes in universes where the characters don't have to be reset and put back in their boxes for the next writer to play with. Cape books, but with a cast that develop somewhat as individuals as well as lists of powers and silly costumes. The "everyone-goes-to-the-pub" issue collected in Lightning Strikes is a particular highlight.
James Roberts is that rare thing – an überfan with the chops to take working with licensing fiction and tell stories that are just plain good with it. Dense character writing plus liberal sprinklings of science fiction concepts plus plot hooks that don't drag on forever before you get some resolved... this guy's the best thing to happen to Transformers in years.