It’s a very interesting one, it’s just that there is a massive gap in the SDMB’s collective knowledge when anything other than geek culture is brought up.
Having said that I won’t have much to add seeing as I read the play ages ago but I think you’re right – a lot of the problem with your ‘getting it’ (and I shouldn’t really worry because plenty of people didn’t get it at the time, and many still don’t) is that there are a few allusions to life and culture in the UK at the time.
For example, there’s the nationality of the two fellows who go to visit the piano guy – Jewish and Irish – it plays on the UK’s complicated feelings of guilt/fear of Jews and the Irish, both of which, like the characters in the play, may have a bone to pick with the country.
The way they treat him, as well, is very like the patter of music hall, and the way in which its half funny, half menacing, adds to the ambiguity of the situation (many music hall comedians played on the Jewishness/Irishness, of course.
Pinter’s plays were amazingly original but they also were greatly influenced by other playwrights whose plays had the same strange menacing surreality, such as Beckett and Ionesco. Reading a bit of them may help your understanding of The Birthday Party.
Seeing the play performed will also go a long way to understanding it, or at least enjoying it, too – all the pauses and repetitions can be hilarious if they’re played that way.
Finally, I think Pinter did want to leave a fair amount of leeway for the readers’/viewers’ own intepretation, as well as create a general atmosphere of strangeness. What you decide is ‘really’ going on will thus say a lot more about you than about the play, and that can be both interesting and chilling.
The play’s recently been revived and there’s a very good review here:
Why not catch a quick flight to London for a performance!