While it's still based on the 2.6 kernel, it's probably good enough for the basics. Not sure there is a more modern source.
(Robert Love's Linux Kernel Programming was also a nice introduction to how the Kernel works, though it might be outdated in some areas now as well)
LDD3 goes way more in-depth and teaches you about the specifics of many different classes of device drivers, their interfaces and data structures, as well as where to find the appropriate in-tree documentation.
(both LDD3 and LKMPG are written for the 2.6 kernel. it's a shame there are no newer resources of the same caliber.)