Hard to say, there’s just so many books out there. The best biography, Clinton Heylin’s 'Behind The Shades, is over 700 pages long. He’s also written two volumes chronicling the origin of each song, ‘Revolution In The Air’ and ‘Still On The Road’ but, once again, they’re quite long, adding up to over 800 pages in total.
I think this would be a good primer. Picked it up before Christmas for some light reading and enjoyed the way it went through album and told his story chronologically.