Cambridge is a great place for bookshops. My favorites include Forbidden Planet, Heffers, Galloway & Porter, and Waterstones, to name but a few. Plus loads of second hand bookshops and market stalls.
Stephen Eldridge kindly reminded me of the old Cambridge bookshop song (TTTO Frere Jacques):Heffers bookshop, Heffers bookshop,But times have changed: Bowes and Bowes is now a Cambridge University Press bookshop; Deighton Bell was taken over by Heffers, and, after Heffers was taken over by Blackwells, closed down, the site curently being a branch of Laura Ashley.
Bowes and Bowes, Bowes and Bowes,
Galloway and Porter, Galloway and Porter,
Deighton Bell, Deighton Bell.
A place that I personally have found good for buying computer kit in Cambridge is World of Computers