How prepared should a critic be when s/he arrives to review a production? Should we be familiar with its history, origins, past productions, earlier versions, and so on – or should we come it to fresh, as many of our readers might? On the one hand, it’s good to be able to reflect the immediacy of the joy of discovery that coming to something completely fresh allows; but are we not supposed to know a little more, so that we can make a better-informed judgement on what is being shown to us today, and how it measures against the past (or not)?
As Charles Spencer notes today in his review of the National’s new stage version of Zola’s Therese Raquin, “It’s a perennial problem. When reviewing stage adaptations of novels, should you read (or re-read) the original before seeing the play? After 30 years on the job, I still can’t decide. You don’t want to seem an ignorant oik when discussing a stage production based on a book many of your readers may already be familiar with. But if you do read the original, it ruins the dramatic surprise.”
So Charlie decided to “skim a few chapters” of Zola’s novel to get the flavour of it – but then found himself drawn in. “As anyone will know who has picked up this astonishing work, it is almost impossible to put down. The French author’s frank and erotic description of an illicit affair, followed by the murder of the adulterous heroine’s husband and the guilt and remorse that follow, is fiction at its most addictive, the novelistic equivalent of crack cocaine. You simply can’t stop until you’ve finished, or at least I couldn’t.”
As a result of this “binge reading”, however, he found that Marrianne Elliot’s production, “though often impressive, intelligent and well acted, seemed like a dim shadow of the thrilling, lurid images already floating around inside my head.”
In other words, the stage couldn’t, in this case, compete with the page; but you could argue that it’s not meant to. Surely a stage adaptation has the right to be judged on its own merits – and should be able to stand alone of prior knowledge of the source — not by comparison with another medium. But we all bring baggage, whether we’ve sought it out or not, to things we see. Theatre doesn’t exist in isolation of other cultural activities, especially when it so often co-opts them for the stage.
This keeps happening with new musicals, so often nowadays based on old films, that comparisons are inevitable. What one hopes for then is a different kind of spark to what makes the film tick – not a slavish recreation (which is the essence of the failure of Dirty Dancing, to find a new theatrical language to transpose its filmic one to).
Of course, some of us are too busy simply going to the theatre all the time to see the films in the first place, let alone read the books, too. But with a genuinely new musical, it’s sometimes difficult to come to a full appreciation of its score on a single hearing. So, again, do you seek out the score in advance if there’s been an original cast album already available, or do you hear it for the first time in the theatre? I love encountering a new score live in the theatre the first time I hear it. But I like to revisit them on CD to make a fuller acquaintance of it, and then try to go back a second time (or more) to see the show again. But doing that, no wonder I haven’t got the time for anything else….!

I'd agree with what you said at the end: I think it's best to go into something fresh with no preconceptions and form an honest opinion. Then do your research to inform that opinion but not change it. Not always practical of course...