I'm asking veteran adventure developer Ragnar Tornquist whether MMOs need to be reinvented. “The MMO genre needs diversity. I think that's what we're saying,” he says. I get the impression he's either nervous or modest.

Or maybe he's both. The Secret World is a modern day MMO in which every conspiracy theory in the world is true. It doesn't feature classes or levels, it's concerned with guns not bows, and it encourages you to search for solutions to its quests on the real life internet. Ragnar continues: “Everybody assumes you have to do one thing. That's like saying Ridge Racer is the only way to do a racer. You might not succeed with everything, but if we look at genres as a single product we'd never have a Call Of Duty, a Crysis, and a Battlefield.”

When I create my character for the game I'm restricted to a few predetermined options. I opt for the classy look – a white-haired chap in a dapper suit. I don't need to worry about bullet penetration or armour buffs – in another MMO-breaking move, TSW's outfits are purely cosmetic. A bit like real life.

The intro is eventful. First, a glowing bee flies into my mouth as I sleep. Then light blasts out of every orifice. Four days later I'm juggling balls of magic as an achingly hip Londoner turns up at the door. She explains that I'm a Templar with powers “beyond what others can imagine”; I've played Assassin's Creed and Broken Sword, so I get it. She's pretty though, and fully voiced, just like the rest of The Secret World's NPCs. Two more factions – the Dragons and the Illuminati – will be available, and all three will battle during PvP in 150-man warzones.

London is TSW's main hub. It's satisfyingly authentic and genre-breakingly detailed. I spend a few minutes staring at bollards, traffic lights and cockney cops before entering a tube station for a tutorial mission. It's filled with zombies that need exploding, and although I'm using a shotgun, I'm also hitting hotkeys and timing cooldowns. This is still an MMO.

I can only choose from one starting weapon, but The Secret World doesn't have any class restrictions. You get XP from killing mobs and completing quests, and points can be spent on any ability, and up to 14 can be equipped at a time. There are no levels either, just an ever increasing move-list. Is Ragnar intimidated by hardcore players breaking his game with an optimal build? He's desperate to see it happen: “We're going to monitor and add new abilities to mix it up. Then a new build will counter this one and the whole thing falls to pieces. Suddenly that flavour of the week has been completely destroyed. Our designers need to have this game live for that to happen.”

Once I'm kitted out, I leave for Kingsmouth – a town laced with horror homage and splattered with the undead. It's a completely different art-style to the London hub, but still teeming with detail. References to Nightmare on Elm Street, Batman and Silent Hill make up most of the street names. Funcom love their in-jokes. They also love investigation missions, which sit alongside traditional collection and killing quests.

I loved them too – at first. Subtle markings on a set of manholes led me to a plaque that mentioned Francis Hals, and a quick Google search let me know that he's a real painter. I found some paintings, clicked one and rejoiced as a new quest kicked in. Using my brain to figure out something real in an MMO made me feel like an awesome detective.

Then the game got mean. Even though I had a journal updated with a new entry and location, I was being led on a fake quest. I'd clicked the wrong flashing, clickable painting. I felt like a shitty detective.

Twenty minutes older, and a bit angrier, I returned to the gallery, exercised my right to first-person, inspected the paintings and found a riddle written on the back of one: “Time is written in the province of kings and gods. The hands of time point to the truth, written by kings in the words of God. The path is open to the enlightened.”

I needed to find a clockface in the town hall, which read ten past ten. Then I looked up Kings 10:10 in the Bible. It's about a lady giving King Solomon 120 pieces of gold. Next, I found Solomon Priest's house, located the entrance to his cellar and typed “120” into the secret keypad, which had space for FIVE digits, not three. He had a locked computer hidden down there. The password? “LUX OMNIA VINCIT” – the words written around the rim of the manholes from stage one of the puzzle.

Of course, no-one really solved this puzzle. It's the riddle of a madman. But thanks to random wandering, and TSW's beta forums, most of us ended up in the right place. The Secret World is an MMO that's eager to innovate and diversify. That's hard. Here's hoping they don't hit too many red herrings along the way.