GUI Tutorial

#1 For the gui system the regular TGB documentation isn't bad.

but you won't find one on how to build a gui system from ground up as thats not a trivial task and also not a too interesting one. people normally use whats there, either in the engine or what CEGUI offers unless they have the cash to afford scaleform

#2 If there is no tutorial on one, then I highly recommend that one be developed for use in the official documentation.