Hi Pat,
Depends on what you want. The Osprey Universal Carrier is an easy read and has some good general info and plates. It runs to their normal format.
For diagrams on stowage I'd recommend the Militay Vehicle Workshop Series Universal Carrier Mk I/II cost about £3.00.
Although it only arrived yesterday Nigel Watson's Universal Carrier Volume 1 looks to be a seriously good book. Photo lead it's packed with information on the Dragon, Armoured MG, Cavalry Scout, AOP, Bren, Lloyd and Universal Carriers. Written for the owners, modellers, restorers and ex-servicemen it would seem to be the bees knees on Carriers. On the front of the Mk I carrier instructions it's highlighted as 'Absolute Reading' by Graham and I have to say just having had a quick look through, there will be more of these getting build over the years lol, lol. It's not cheap, I think mine was around £30.00 from Waterstones.
If plastic model manufacturers can't see the potential in this vehicle and it's variations well .......lol, lol.
The Tamiya kit may be old but Resicast's new conversion sets have breathed a complete new lease of life into it IMHO.
Cheers and happy modelling.
Al