No, I'm not sure why it's called Sparko. It's a mystery!
The main character of the book is a young man (who looks like a boy) called Norman Niemand (which means "nobody," because Stephan is just that clever!) who was once a big rock star but who is now a junkie who sells drugs to the dregs of society. Apparently seven years ago the love of his life, Amy, died in a car accident, which sent him into a spiral of depression. One night he runs afoul of his supplier, Bragg, who has one of his flunkies stab Norman and dump him in the Thames. Problem solved!
Except, of course, that Norman doesn't die. He washes up on the shore and meets Belle, a young lady thief who's running away from three old spinsters and their horrible dogs, which includes a bouncing, evil Pomeranian (it's that kind of book). Norman won't let Belle get away, because she has a pendant that Amy used to wear and he doesn't know where she got it. She takes him under London, where the outcasts and supernatural weirdos of London live. It's an interesting notion, actually - London can't forget all the tribes and armies that conquered her, and traces of those events live on underneath her (presumably because there are so many layers underneath today's London), where they gain consciousness but become twisted versions of themselves. There's the embodiment of Boudicca, for instance, who has been turned into a being called "Empire" and who resembles Margaret Thatcher, unsurprisingly.
Belle had to retrieve a relic because the Underground Queen's son, William, was kidnapped and the goblins who took him wanted the relic. Nothing, of course, goes right. Eventually it's revealed that it's a big scheme to return a pagan monster banished by St. Augustine of Kent back in the days when he established the archbishopric of Canterbury back in the 590s. Because that's what you do!
Stephan does care about the plot, but he also makes sure that he gives us a lot of colorful characters. Norman and Belle are interesting, not because they have a romance, but because they seem to be the typical "antagonists who eventually grow to like each other," yet Stephan makes sure that it doesn't really go that way. Norman is too much of a dick, and Belle is too much of a thief. Norman's journey is fascinating, because we think there's more to his story about Amy, and there is, but what we learn makes him far less sympathetic, which makes his acceptance of his douche-baggery more powerful. The third main character, I guess, is Harry, a Templar with an attitude, who helps Norman understand what he's been doing with his life. (Stephan's character design for Harry is hilarious - at one point he takes off the wig we didn't know he was wearing to reveal his baldness, and Stephan writes in the back matter that he got sick of drawing his hair style, so he just had him take it off.) The villains are done quite well, too - I won't reveal the main villain, but he's cruel and vile and rather interesting. The book has some humor in it, but Stephan is also more concerned with what happens to people who are forgotten and what happens to people who can't forgive themselves. There's a nice bit at the end where Norman realizes that his situation hasn't changed all that much, and he finally decides to change himself.
Stephan's art is really beautiful - full of goofy and/or nasty characters, each with plenty of personality. His "underneath London" landscape is a surreal mix of actual architecture and weird, demonic buildings.
Stephan crams the book with oddball stuff, so that we feel like Norman really is navigating a strange netherworld. His Norman does look a bit too young (he's rather small to begin with, but he has a boyish face to boot) to the extent that Belle, who's the same size as he is, looks far older and gives their nascent not-quite-friendship/not-quite-romance an odd vibe. Stephan does nice work with the horror parts of the book, as his nasty creatures are just bizarre enough to not be too scary but weird enough to be unsettling. His giant monster at the end actually is somewhat scary - a nice, lurching thing from the depths of the earth that doesn't appreciate humanity in the least. A great deal of the humor of the book comes from the odd juxtaposition of the mundane with the fantastic, and Stephan pulls it off really well.
Sparko is a cool little comic - it's full of high adventure and weird supernatural doings, but it also has a lot of humor and deals with some serious themes as well. Stephan is a good creator - I'll have to keep an eye on him. For now, I'll just Recommend Sparko to you. The title might not make sense to me, but the comic is good!