Just finished this really useful little book: "Medina in Birmingham, Najaf in Brent: Inside British Islam" by Innes Bowen. It could well be subtitled "An executive summary of Islam in Britain", because that's exactly what it feels like - a brief, breezy and dispassionate summary of the main Muslim groups in the UK, what they believe, how they interact with the world, etc.
Very handy reading, if you're a non-Muslim British person like me who might be wondering: the Muslims in my neighbourhood, are they sunni or shia? Does it matter? How do they relate to the various Muslim groups that are making the news these days? Which ones dress in special ways, and how significant is it? - All those naive questions that you can't just come out and ask.
All kinds of interesting stuff comes up while answering these questions. For example I learnt about the Tablighi Jamaat and why they wanted to build the "mega-mosque" that has been back and forth in the news trying to get planning permission. I learnt which groups have a voice in the Muslim Council of Britain. And even though the book doesn't spend much time on women's issues, it gives lots of titbits about different groups' conventions on veiling, staying in the house, marriage, and mosque provision - so it gives me some "local" insight to complement this other reading on veiling practices.
As in that other book, one thing that might surprise you is that some seemingly "traditional" things (like clothing practices) are borne of quite modern movements within Islam; really, you realise that "traditional" vs "modern" is not a particuarly helpful way to distinguish different strands of Islam practiced in Britain today.