In a small, windowless room away from the crowds at the Barcelona foundation built to maintain the legacy of Joan Miró there is his library. It contains poetry, of course, as well as Plutarch, Hemingway and Lewis Carroll. But on the same shelves there are other books – the pulp fiction thrillers of Edgar Wallace; the schlocky master criminal Fantômas novels; a David Lodge; an unread Ulysses.

It says a lot. For such a wildly imaginative, radical artist there is lots that is reassuringly everyday about Miro. He had a very happy, stable marriage. He was extremely organised. He wasn't known as a big drinker or party animal. In photographs he has no Picasso or Dali-like swagger. He looks like a slightly apprehensive accountant, worried that he's mislaid some receipts.

But it is his art that makes Miró the titan that he is. Next month Tate Modern in London will stage the first major UK exhibition devoted to his work for nearly 50 years – a remarkable gap which, Tate hopes, will mean an entirely new generation can have their eyes opened to one of the most important of all 20th century artists.

The show, which will travel to Barcelona and Washington, also aims to confound expectations and explode a few myths. "Miró's work is often understood in ways that are a little simplistic," conceded the show's co-curator, Marko Daniel. "People look at his work as if it were childlike, or childish, and they tend not to see the depth of passion that goes into it."

Today Miró, a genuine pioneer and forefather of abstract expressionist art, is revered in Spain. Not as a hero necessarily but as a great man whose presence in his home city of Barcelona is everywhere.

It was not always the case. During most of the Franco years Miró was better known abroad. "He went from being almost entirely invisible in the Spanish art world to being feted as the greatest living painter in Spain," said Daniel.

It is also said that he did not really involve himself in politics, living his later years in a kind of self-imposed internal exile under Franco. That may have been true but, the show will argue, it does not mean that Miro was unengaged.

"Throughout the years of internal exile he engaged in a very deliberate process of resisting approaches from the Franco regime which wanted to involve him in representing them abroad. He refused to take part in state-organised exhibitions."

The show will draw heavily from the foundation he helped create back in 1975. The building's modernist beauty and grandness is a reflection of the adoration that Miró is held in by Barcelona.

Fly into what is now terminal 2 of the airport and you can't miss the enormous ceramic mural which looks as stunningly, vibrantly fresh as it did when he installed it with his lifelong friend Josep Llorens i Artigas in 1970.

In the city itself there are the mosaic tiles he designed, walked over by thousands of tourists on a part of Las Ramblas. Or the many artworks that dot the city including, in Parc Joan Miró next to the old municipal slaughterhouse, one of his last sculptures, the 22-metre (72ft) high Woman and Bird. But it is the Joan Miró Foundation that has so many of his works and keeps the flame burning for Miró. There are more than 200 paintings, 178 sculptures, textiles, ceramics and around 8,000 of the drawings that Miró assiduously kept, going back to when he was an eight-year-old.

The foundation helps paint a picture of an artist who is striking not just for the quality of his output, but the longevity.

This is a man who was collaborating with Max Ernst in 1926, designing for Diaghilev's Ballet Russes, and in 1978 designing grotesque puppets for a collaboration with the experimental theatre company La Claca called Death to the Bogeyman (a reference to Franco).

Miró was born to reasonably well-off parents in the old town of Barcelona in 1893, 12 years after his friend Picasso and 11 before Dali. Like most young artists of his day, Miró had to be at the centre and that meant Paris. It was here that he fell in with the wrong crowd, or poets at least.

But what an effect it had on him. He was galvanised and completely changed his working practices, abandoning figuratism and embracing surrealism. This most mild-mannered of artists was now proclaiming that he wanted to "assassinate painting".

In 1956 Miró settled in Palma, Majorca, home of his wife, Pilar. The Fundació Pilar i Joan Miró was created in 1981, and visitors can see the artist's studios and methods of working as well as a good many works in the permanent collection.

As you walk up to the studios there is the sound of Turner prize winner Susan Philipz singing Roxy Music's More Than This, a commission from 2007 that fits the beautiful setting overlooking the Mediterranean.

Inside the studios visitors are first struck by Miró's graffiti-like drawings on the whitewashed walls, rapid expressions of his ideas that have the look of cave paintings but would become bronze sculptures or ceramics.

There are, of course, paint splashes everywhere, and Daniel and his Tate co-curator, Matthew Gale, get visibly excited as they work out where in the room some of his most famous works were executed.

In another light-filled space there are paintings everywhere, reflecting how Miró would often leave a work for years before finishing it.

The Tate show will not be an exhaustive retrospective, although it will have something like 150 of his works.

Above all, it will address his political engagement, one that has sometimes been called into question.

Given the times he lived in and "his extreme sensitivity both to the poetic and to the social and political", said Daniel, "it's not that we are making the claim that he was politically engaged but he could not be anything but.

"In all the work he produced the social and political is always there at one level. He was fully attuned to the world around him."

Joan Miró: The Ladder of Escape, at Tate Modern 14 April-11 September