A (very) brief history of the ILP
The ILP was formed in 1893 as the Independent Labour Party in order, as the name suggests, to set up a Labour party genuinely independent of the Liberals, who were the main Parliamentary opposition to the Conservatives at that time. It was a co-founder of the Labour Party, and many of the major figures in Labour's rise in the early part of the century were ILPers.
Pictured: George Orwell
In 1932, the ILP left the Labour party over its relations with the Parliamentary party in the wake of the setting-up of the National Government (though the divisions ran deeper). It remained a significant political force throughout the 1930s, and had a small but vocal parliamentary presence until 1946.
In 1975, after several years of debate, the ILP changed its constitution and returned as Independent Labour Publications to the Labour party. Today, it is an educational trust, publishing house and pressure group committed to democratic socialism and the success of a democratic socialist Labour party.
If you want a fuller introduction to the ILP's history, you can't do much better than read Barry Winter's The ILP Past and Present, about which you can find out more on the publications page. Among other books about the ILP, its history, its main historical figures and the movements of which it has been part, you may find the following interesting (they are not available from the ILP):
Caroline Benn, Keir Hardie
Fenner Brockway, Inside the Left
Fenner Brockway, Socialism over sixty years - the life of Fred Jowett of Bradford (1864-1944)
Gordon Brown, Maxton
David Clark, Colne Valley - radicalism to socialism
R E Dowse, Left in the centre
June Hannam, Isobella Ford
James Hinton, Protest and visions: peace politics in 20th century Britain
David Howell, British workers and the ILP 1888-1906
David James, Tony Jowett & Keith Laybourn (eds.), The centennial history fo the Independent Labour Party
Keith Laybourn and Jack Reynolds, Liberalism and the rise of Labour
Jill Liddington, The life and times of a respectable rebel: Selina Cooper, 1964-1946
Jill Liddington and Jill Norris, One hand tied behind us
Alan Mackinlay and R J Morris (eds.), The ILP on Clydeside: from foundation to disintegration
David Marquand, Ramsay MacDonald
Keith Middlemass, The Clydesiders
Kenneth O Morgan, Keir Hardie, Radical and Ssocialist
George Orwell, Homage to Catalonia
Henry Pelling, The origins of the Labour party
Henry Pelling, A short history of the Labour party
Ben Pimlott, Labour and the left in the 1930s
Gred Reid, Keir Hardie: the making of a socialist
Jon Schneer, George Lansbury
Sarah Stanley Holton, Feminism and democracy
Carolyn Steedman, Childhood, culture and class in Britain: Margaret McMillan 1860-1931
E P Thompson, Homage to Tom Maguire, in Briggs and Saville (eds.), Essays in Labour history vol. 1
Chusichi Tsuzuki, Tom Mann: the challenge of Labour
Joseph White, Tom Mann
Ian Wood, John Wheatley