Marmite: It's spreading all over

Yeast extract: black, sticky, sludgy sort of stuff, made from breweries' left-over slurry. Has anything else this unpleasant-looking and sounding had such a stranglehold over the minds and mouths of Britain? But we're not just talking yeast extract here, we're talking Marmite. And right now we're having a bit of a Marmite moment.

Marmite seems to be everywhere, on everybody's lips (quite literally, if they're in the love-it camp). A pop-up shop has just opened on Regent Street, dedicated to the ever-growing range of Marmite-branded products, from yellow-and-black sandwich boxes to "J'adore/Je déteste Marmite" T-shirts. Marks & Spencer have recognised the loyalty it inspires, and they announced at the start of November that they'll be stocking brand-name items. As John Dixon, their food director, explained: "There are some products that we could simply never compete with, like Marmite". ECP Design's cake tins and crockery decorated with pop-art, multicoloured versions of the classic Marmite design have been a big hit, netting a Gift of the Year award. Marmite-flavoured cashew nuts, rice cakes and cheese, which already adorn our supermarket shelves, have just been joined by a breakfast bar, which Unilever's brand manager, Noam Buchalter, claims is "the world's first savoury cereal bar".

Fans would argue all the fuss is deserved, that the brown-black goo in a squat little pot is no mere toast topping, but a symbol of Britishness, hailed as a design icon and possessing a uniquely divisive taste.

Style guru Peter York, who admittedly "detests" Marmite, argues that this is all just clever marketing: "I don't think it is such an 'iconic' brand. Our iconic-ising of it must have started in the late 1990s, when they introduced very visible advertising for such a small brand. You have to admire whoever came up with the love-it-or-hate-it idea, because that's what all this marketing is piling up on: it's an advertising driven brand momentum, a new phenomenon for our times."

So are we actually just having a marketing moment? Maybe not: the love/hate thing is really just the tip of the iceberg, the yellow lid on a big treacly pot of trivia, as two new books have revealed. Maggie Hall, a former journalist, has recently published The Mish-Mash Dictionary of Marmite: an anecdotal A-Z of 'Tar-in-a-Jar, while the official Unilever option – The Bumper Book of Marmite – goes on sale in December. Both are stuffed with intriguing stories about Marmite.

Although obviously falling in the Marmite-loving camp, Maggie explains she wasn't an obsessive before she began her trivia-tracking. But once she started, she was "totally amazed" at the stuff she dug up. From Marmite's medicinal properties (it's so packed with B vitamins that the Red Cross included it in their prisoner-of-war parcels) to its popularity with animals (cats, ferrets and parrots all feel the love) to its contemporary use as a cheeky slang term (as in "talking a load of Marmite"). "I had no idea that Marmite had such a grip on our palettes and on our minds."

We might think of Marmite as a British thing, but it was developed by a 19th-century German chemist, Baron Justus von Liebig, and there are fans around the world: there's a Marmite museum in Missouri, and Yorkshire-born NASA astronaut Dr Nicholas Patrick chose the spread as his one comfort food item on board a 2006 shuttle flight. They don't use knives in space though, so he had to make do with the controversial squeezy bottle.

Controversial? Oh yes, Marmite fans are very protective of their favourite foodstuff. While special editions are snatched up with delight (few presents have been as well-received as the 2008 Valentine's champagne version given to one Marmite lover) and have become e-bay staples, newfangled updatings may be greeted with downright hostility. Unilever cleverly averted this in 2006 by promoting the squeezy version with a "MarmArt" exhibition: artist Dermot Flynn painted portraits of love-'em-or-hate-'em figures such as Simon Cowell, Margaret Thatcher and James Blunt (guess they were appealing to the hate-'em camp mostly, then) on little toast canvasses using – what else? – squeezy Marmite.

Maggie also cites this newspaper as revealing the full extent of the British passion for the salty spread: after an article published in 2006 described the perfect way to make Marmite on toast, we received hundreds of letters and e-mails. Consquently, between 31 August and 14 October, at least one piece of Marmite-mail was printed every day.

The humble extract has also "left its place on the breakfast plate for the upper echelons of fine dining", Maggie says. Michelin-starred chef Sat Bains swears by it, while gourmet chocolatier Paul A Young does a fine line in Marmite truffles. The Bumper Book also divulges details of Gary Rhodes' Marmite ice cream flavours, and reveals that Marmite is a special ingredient in Vegetarian Pot-au-Feu, one of Heston Blumenthal's creations served at the Fat Duck.

This faith in the ability of the right recipe to sway Marmite-haters reveals the desire of fans to convert non-believers. Marmite can even become a personality test: at a recent late-night snacking session with some new friends we were relieved to find that we were all Marmite-lovers. For those who consider it some kind of god-given elixir (and the face of Jesus did appear on the lid of a Marmite jar in Wales last May), the discovery that someone won't go near the stuff can be a bit like finding out they vote Conservative or only read Dan Brown novels.

Maggie has clearly overcome any bias against Marmite haters though: her husband is an American who loathes it. Luckily for him, the Mish-Mash Dictionary is not just for fans. It also describes the alarming allergic reactions Marmite sometimes prompts in babies, and points out the similarity between the dark-brown gunk and pus from diseased pigs. So Maggie is right to claim there's "plenty of ammunition" in her book for those who hate the mere sight of the pot-bellied jars. Which is probably just as well, because the haters are going to have to put up with Marmite-mania for a while yet.