Just a very funny, sincere, very well acted comedy. For Brits of a certain age, the 80s references and nostalgia are spot on, much of it too obscure I'm sure for those not there at the time to appreciate fully.
Much of the comedy comes from two ongoing situations: the catty relationship between Alan's mum and the neighbours who live opposite, which mainly consists of a trade in (sharply witty) back-handed insults, and the other situation of course being Alan's campness, oddball unconformity, his path to discovering that he is gay.
A couple of reviews here have given totally unjust 1 ratings, citing that it's just a one trick gag which wears thin, but I didn't find that at all. I was chuckling throughout every episode. The campness of the young Alan is so well done, and the writing so on point, that it remains funny even after 12 episodes.
I'm not sure how non-Brits will receive this comedy, maybe it works fine, but I would highly recommend for Brits anyway.
Writing this having watched two seasons, and glad to hear that a further two seasons are planned.