Links to epubs/pdfs of Blur books and some related Britpop ones:
Blur: 3862 Days - Stuart Maconie
The best Blur book, it comprehensively covers their history up until 1999. I've heard there is a newer edition that goes a little bit further but I've not managed to find that.
Bit of a Blur - Alex James
Alex's first autobiography and own account of the bands history, plus a lot of bars, booze and cocaine.
All Cheeses Great and Small - Alex James
Barely mentions Blur tbh, it's mostly focused on his life as a farmer. Unless you really like his writing I wouldn't bother with this one.
Verse, Chorus, Monster - Graham Coxon
Graham's recent autobiography. It covers quite a lot of Blur's early history, then obviously skips the parts he doesn't want to remember so much. There's a lot of side bits about his art and learning guitar techniques.
The Life of Blur - Martin Power
This one covers Blur up until about 2013. He didn't interview any of them directly, but spoke to people who knew them and took a lot from archives and historical interviews. I learned some new things, pretty decent.
Black Book: The Live History of Blur - Drew Athans
This is an interesting book that reviews live recordings of a large chunk of the bands history up til 2009. The 2nd edition print version goes up to 2012. I find it really interesting from a research point of view, and you can find most of the recordings discussed on the Blur Archive Project
Damon Albarn: Blur, Gorillaz and Other Fables - Martin Roach
This is obviously Damon focused so covers his side projects as well as Blur. Some of it is a rehash of what can be found elsewhere, but still had some unique bits.
The Last Party: Britpop, Blair and the Demise of English Rock - John Harris
This encompasses many bands around the Britpop scene but obviously Blur feature quite heavily. Gives you lots of useful contextual info
Just For One Day: Adventures in Britpop - Louise Wener
Louise from Sleeper's autobiography, it only briefly mentions Blur but I'm including it because it's quite a nice little easy read with lots of vignettes from someone in the middle of Britpop.