There are dozens of different guide books to London. I'm not going to list them nor am I going to pick any in particular. There are numerous websites, too, for guides and tips on London. Rather than carry a heavy guide book, photo copy the pages you're interested in and bring them. Or, if you have a smart phone, iPod, netbook, iPad or the like, check out applications or load on pdf maps, podcasts and guides for reference. They take up a lot less room.
I have an old guidebook to London that was published during World War II. There's a small insert piece of paper that explains that due to the war, they cannot publish the full set of maps they usually do. There is only one fold out city center map with the underground stations marked and some of the main streets.
What really makes me laugh, though is their suggestions for itineraries for one or two days' sightseeing. I really don't know how you could fit it all in! Surely they don't suggest you do all these things? I wonder if they're saying that any or several of these for morning and afternoon would be sufficient though they do mention that it's a "very hurried day". I expect you could do it if you were just walking past all these sights and not going inside. To reproduce it:
One Day. Morning:
National Gallery, National Portrait Gallery, Whitehall (passing Gov't Offices, Royal Unitied Services museum and the cenotaph), Parliament, Westminster Abbey and cathedral, Buckingham Palace (exterior), St. James's Park, London Museum Lancaster House, St. James's Palace (exterior).
Lunch in the Piccadilly or Leicester Square area. (phew!)
Afternoon: Regent, Oxford Streets, Wallace Collection, Drive thru Hyde Park, Kens. Gdns, Piccadilly, Royal Academy, British Museum, Lincoln's Inn walk, Law Courts and Temple, Fleet Street, Ludgate Hill, St. Paul's
They go on to suggest dinner and theatre if you are staying overnight.
An Alternative might be:
Twr London, Monument, Bank of England, Royal Exchange, Guildhall, Cheapside, St. Paul's. Lunch. Law Courts, Temple Gardens, Embankment, County Hall, Parliament, Westminster Abbey, National Gallery (open evenings of certain days).
A bit more doable.
A suggestion for a two day visit:
Charing Cross, National Gallery and Portrait Gallery, Whitehall, Parliament, County Hall, Westminster Abbey (Lunch) War Museum, Lambeth Palace exterior, Tate Britain, Westminster Cathedral, St. James's Park, London Museum, Green and Hyde Parks, V&A museum, Nat. Hist. and Science Museums.
Twr. London, Monument, Royal Exchange, Bank, Guildhall, Cheapside, St. Paul's, (lunch) Holborn, British Museum, Oxford St., Wallace Collection, Regent's Park, Zoo
Longer stays suggest things like the Dulwich Picture Gallery, the "new" Horniman museum, Windsor, Hampton Court, Kew, Richmond, Epping Forest, Croyden Airport
Oh yes, that's the main international airport, Croyden. In another old book i have, published in the 50's, it mentions London Airport (Heathrow) that is under construction. In that book, the Museum of London has moved to a wing of Kensington Palace.
Old guidebooks are fascinating!