British Library - Have been associated this for ages as my dad is closely attached with the board. I have volunteered for their educational fairs that happen in India every year. They have amazing collection of books. Huge library with every and all kinds is subject books. A subscription is required initially which is worth the payment if you are a book lover. name a book and you would find them here. One of the biggest libraries with biographies too. must visit. Kids also have good collection of books to enhance their mental ability ..many books are available on Mathematics too...do visit and am sure it's worth the payment done for membership.