There are books about television and there is television about books, but the relationship between the two has always been a little strained.

Books rather look down on television, like it's an embarrassing and vulgar relative, while television behaves towards books like an abusive boyfriend: it uses books shamelessly, mainly as material for adaptations, and then when it's finished, moves on to something sexier.

The Secret Life Of Books (BBC Four, Tuesday, 8.30pm) is an exception: it is a tribute to reading and books that is so referential it practically gets down and sniffs the pages.

Last week the love reached new heights when it looked at what is, after the Bible, arguably the most important book in the entirety of British culture: Shakespeare's First Folio.

The problem is that no one really knows precisely what the First Folio is.

We know it is a collection of around half of Shakespeare's plays, but it was published after his death and appears to include plays that were at best half-finished - Timon Of Athens for example.

Were these first drafts? Were they collaborations with other writers and never intended as the final version?

Even the "to be or not to be" speech from Hamlet included in the Folio is one of several versions that are known to exist.

In an attempt to dig down into the truth, Simon Russell Beale, the presenter and great Shakespearean actor, explored three plays from the First Folio in more detail: Timon, King Lear and Hamlet.

What he discovered could be seen as evidence of Shakespeare's personality and disposition, at least while he was writing the plays.

Beale's conclusion is that Shakespeare, for whatever reason, was not in a good place when he wrote Timon and Lear.

Famously, Timon is just one long rant, but the story of Lear is even more interesting.

As he usually did, Shakespeare took the story of Lear from an earlier source but the first version had a happy ending with the king reunited with his daughters.

In Shakespeare's version, Lear is mad and Cordelia dies.

It's a bit like taking a happy-ever-after fairytale and giving it a tragic ending; it's a bit like taking Goldlilocks and having the three bears rip her to pieces and eat her.

Beale believes that this darkness in the plays was because of the darkness of Shakespeare; he even believes that, such is the bleakness of Lear and Timon, that Shakespeare may have been depressed. What Beale does is explore the history of a great book but he also performs a diagnosis on a 500-year-old patient. It makes us appreciate Shakespeare all the more, but feel a little bit sorry for him too.