This Sunday, 23 April, St George’s Day, traditionally Shakespeare’s birthday, 12 copies of the exceedingly rare first edition of his plays will go on public view around the country. The book first appeared in print under the title of Mr William Shakespeares Comedies, Histories, & Tragedies in 1623, seven years after the author’s death. Known as the First Folio, it is the apple of auctioneers’ eyes. The initial print run was for 750 copies; only just under a third of them are known, though every two or three years another will emerge, in various states of disrepair, to the enormous enrichment of its owner. The Folger Library in Washington DC, determinedly collecting copies between 1893 and 1928, has no less than 82, a third of all known copies worldwide; in the British Isles there are 50.

This book, the purpose of which was to collate all of Shakespeare’s plays into one readily accessible volume, was single-handedly responsible for the survival of 18 plays which would otherwise certainly have disappeared from view, among them such trifles as The Tempest, Julius Caesar, Twelfth Night, Measure for Measure, All’s Well That Ends Well, Antony and Cleopatra, As You Like It, Coriolanus and Macbeth. The editors’ declared intention was to publish the plays “according to the True Originall Copies”, replacing “stol’n and surreptitious copies, maimed and deformed by frauds and stealths of injurious impostors”.

Less than half of Shakespeare’s plays were published during his lifetime, most often in indifferent, slipshod editions. This sumptuous collection, 950 pages long, was a posthumous assertion of Shakespeare’s supremacy as a dramatist. The editors were neither scholars nor publishers – they were actors, Shakespeare’s fellow players and friends, John Hemminge and Henry Condell, both named in Shakespeare’s will.

Undertaking the daunting task of tracking down decent copies of 18 plays, many of which had fallen out of the repertory, most of which would have existed only as individual parts, was little short of heroic: they were required to become not merely publishers – a demanding job in the low-tech world of Jacobean printing – but also sleuths.

The great objective of the First Folio was to celebrate – indeed to introduce in propria persona – the elusive author who, seven years after his death, was in danger of falling out of fashion. The title page features a vivid and unidealised portrait of him by the fashionable Huguenot engraver Martin Droeshout. Shakespeare’s friend and rival Ben Jonson, in an address to the Reader, praises its accuracy, but with a reservation: “… the Graver had a strife / With Nature to outdo the life: / O, could he but have drawn his wit / As well in brass, as he hath hit / His face the Print would then surpass / All that was ever writ in brass. / But since he cannot, Reader, look / Not at his picture, but his book”. In other words, that’s exactly what he looked like, but it doesn’t capture his personality.

This nonetheless is the image of Shakespeare that the entire reading world has ever since lodged in its mind; for me the picture of a neurasthenic, puffy-eyed figure in the portrait is entirely credible: a man who seems to be a stranger to sleep, his brain incessantly teeming with images, emotions and conceits.

There follow laudatory poems by minor poets which are charming and personal, but Ben Jonson pulls out all the stops, telling us that “the Swan of Avon” was “not of an age, but for all time”, that he stands with the greatest writers of antiquity and surpasses those of the present, appreciated by his royal patrons as much as by the common man: “what a sight it were / To see thee in our waters yet appear / And make those flights upon the banks of Thames / That so did take Eliza and our James!” Quite something from a man not noted for his generosity to his fellow writers, though he can’t refrain from ribbing him for having, famously, “little Latin and less Greek”.

Hemminge and Condell, in their introduction, speak affectionately of Shakespeare as a colleague, of his punctual and impeccable copy. The appended list of those who acted in the plays is headed by Shakespeare. What he played – what any of the actors played – we don’t know; but he was clearly an active company member.

All of this adds up to a vivid account of the writer, the actor, the shareholder, the colleague. There is nothing about his background, his family or his life; we still know very little about these aspects, as we do of his contemporaries. In the end, of course, it is the writing that matters.

In due course, the First Folio was supplemented, in second, third and fourth folios, by texts newly come to light, few of them actually by Shakespeare, but it is the 1623 edition that over subsequent decades has occupied an absolutely central role in our connection to the playwright. Some of my colleagues have an almost religious devotion to it, feeling that it brings them close to the source. Personally, I have never felt any great desire to look at a copy. I knew, I felt pretty sure, what was in it; the rest was surely fetishism. So it was in a spirit of only mild curiosity that I accepted the kind invitation of the City of London Corporation Library at Guildhall to see their copy, widely considered to be among the very best extant, undamaged, unannotated, not remade.

There it sat, unremarkably, on an orange cushion on a bookrest in the centre of a room which happens to be in direct view of the site (now part of the Barbican) where William Jaggard printed it; in full view, slightly to the left, is the statue of Hemminge and Condell, on the site of the church, St Anne’s, where they are both buried; and a mere stone’s throw from the old St Paul’s Cathedral where, in the early 17th century, the booksellers plied their trade, and where you could have, if you were in possession of the princely sum of 15 shillings, bought an unbound copy. If you were part of the Jacobean plutocracy, you could buy a bound edition for a pound.

Whether it was finding myself at this strange confluence of historical locations, or a sudden sense of awe at being in such close proximity to this astonishing tome, I suddenly felt intensely emotional. Peter Ross, the head of collections, invited me to turn the pages – shiny, sturdy pages – and I began to feel a powerful connection, not so much to the author, but to the readers and audiences who first heard these words, and to the actors who spoke them. Jacobean orthography is easily understood and I found myself reading out loud a scene from As You Like It, then a few ribald phrases of Falstaff’s, and finally Henry V’s St Crispin’s Day speech, with its ringing rhetoric and its incomparable music. “And Crispin Crispian shall ne’er go by / From this day to the ending of the world, / But we in it shall be rememberèd— / We few, we happy few, we band of brothers / For he to-day that sheds his blood with me / Shall be my brother; be he ne’er so vile / This day shall gentle his condition.”

That was what did it: my eyes filled with tears, my voice shook. I “drowned an eye,” as the Sonnet says, “unused to flow”. It was if I had never spoken a word of Shakespeare’s before.

This miraculous book is the most direct connection we have to the master who wrote these words, to the language as it then was, to the human life in all its complexity which on every page it celebrates. See it while you can. Take your children and your grandchildren. This an experience that no one who cares about the life of our culture can miss.

• You can see the First Folio in locations across the country from 23 April