Hey, nothing can beat a good book for me! I like read when I'm on bed or when easily sitting on my wc cup
Serious, Book is many things:
1) A status. All major application has a dedicated book. It is a prestige for the software and for the company. I.E. blender has many books dedicated, and other will release.
2) A book is a big work and worth all single penny IMHO. It is not a 1 hour DVD, where a guy talks on a fast video. A book can be really study, can write on his pages, can turn back and read easily complex passage you need and can doing all without a pc.
3) It is really nice when you have your library reference, old and new books can be consulting anytime you need some info. DVD is really a different format and not so easily
I think needs all (DVD, Internet (fast update resource) and books)
the community book look really nice IMO