At 8am on Saturday Oxford’s Weston Library will open its doors and a new chapter in the 412-year history of the Bodleian.

For some months now readers and researchers have been enjoying fruits of an £80 million scheme that has seen the transformation of the New Bodleian, that vast fortress of books on Broad Street.

Now, as the Weston, it is a vastly different place: light, modern and with the vast Blackwell Hall, the 15.5m high entrance foyer, filling space created by the removal of the 11-storey book stack that had stood in the heart of the building.

But this weekend, to celebrate the renewal of the Gilbert Scott Grade II-listed building, the public is being invited to enjoy behind-the-scenes tours, displays and lectures about the refurbishment and building work over the past three years. The programme of events over Saturday and Sunday will coincide with next weekend’s launch of the Oxford Literary Festival.

But perhaps the real significance is that those passing through the doors will only be the first of thousands in the coming years, with the Bodleian effectively creating a new Oxford visitor attraction.

That is not to say tourists are being allowed to mount a wholesale takeover of the Republic of the Learning. The great library building will be still predominantly for scholars and researchers. But with millions of books having been moved out to a huge book depository at Swindon, space now exists for the public to enjoy this extraordinary building and enjoy the library’s great treasures in a variety of exhibition areas.

For the Bod’s special collections include some of the world’s most important cultural, intellectual and scientific treasures. The new era of public access will start in eye-catching fashion, with the weekend seeing the opening of the Marks of Genius exhibition, which will run until September 20.

In what amounts to the Bodleian’s greatest hits the exhibition will include Shakespeare’s First Folio, an original draft of Mary Shelley’s Frankenstein, the 1455 Gutenberg Bible and the dust cover of The Hobbit, designed by Tolkien.

An undoubted highlight will be Magna Carta, on display in the birthplace of King John, exactly 800 years after he put his seal on the document seen as the foundation of liberty in a meadow beside the Thames. The Gloucester Magna Carta, dating from 1217, will be on display at the library, which holds nearly a quarter of the world’s original 13th-century manuscripts of Magna Carta.

But for many the biggest attraction will be the Weston Library itself, with the ultra-modern library on the corner of Broad Street and Park Road – already dubbed the Mod Bod – unrecognisable, at least inside, from the building opened by King George VI in 1946 – an occasion that did not go entirely smoothly, with the ceremonial key breaking in the lock, meaning the King and Queen were only able to enter after much pushing and shoving. (The key, cased and still in its broken state, is now counted among the library’s treasures.) Richard Ovenden, Bodley’s Librarian, said: “This project has been an amazing opportunity to transform an unloved library building at the heart of Oxford. In a city full of libraries, it is one of the most significant and exciting library transformations for many years.

“We are particularly delighted to be able to welcome the public into the Weston Library, to help them appreciate and enjoy the collections built up in the university over centuries, and to engage with the ground-breaking research which surrounds these collections in Oxford.”

Lead architect Jim Eyre was the driving force behind the project to breathe new life into the 1930s structure. Last month, Mr Eyre, co-founder of the leading architectural practice Wilkinson Eyre, was presented with the Bodley Medal, awarded to individuals who have made outstanding contributions to literature, culture, science or communication.

Mr Eyre became the first architect to receive the medal, first engraved in 1646 to honour Sir Thomas Bodley, the founder of Bodleian Library. It has previously been presented to Wolf Hall author Hilary Mantel, writer Alan Bennett, the film director Richard Attenborough, author PD James and the world wide web inventor Sir Tim Berners-Lee.

Mr Eyre said the design aimed to celebrate the library’s precious objects and “to protect the future of this cultural and intellectual landmark”.

The building has not always been described in such glowing terms. The great travel writer Jan Morris famously compared it to “a well-equipped municipal swimming pool”, while others saw it as “prison like”.

Steps on Broad Street now lead into a new entrance colonnade with glass doors on the south side of the building. But the pivotal decision was to clear out most of the core of the building from the ground floor up, with three storeys of book stacks retained in the basement, providing 39km of storage space for 1.4m volumes of rare books, manuscripts and maps. Before its closure the 11-storey New Bodleian had housed some 3.5m books.

Blackwell Hall, housing the new Bodleian cafe and information desk, open to the public, occupies most of the ground floor. In the future it will be able to host events, accommodating 250 seated and 450 standing.

Two exhibition galleries and a new lecture theatre are close to the hall, from where hall visitors can look up to see an innovative glass-sided floating stack, providing glimpses into the inner workings of the library. The hall will also feature displays like the newly conserved 16th-century Sheldon tapestry map.

During my visit, Sabina Pugh a senior book conserver, was hard at work on a 13th-century bible covered in red velvet. “We think it was once owned by Archbishop Laud,” she said. “But it certainly came from Henry VIII’s library.”

The building, if not the books, may now look new, with natural light now flooding into Gilbert’s Scott’s once darkened unloved structure. But the radical makeover serves only to show more clearly why this landmark of learning deserves to be treasured by the whole city.