Oh, congrats! In the meantime when I wrote my last posting you were lucky to catch that 15"DSDL Book. Great!
While you're waiting for delivery you may have a look at MacintoshGarden to check out Tiger/Leopard/os9.22 and other software-gems ..
There are also some other great repositories for PPC Mac-software - I cannot recall their names and links out of my memory, since I've collected/downloaded all PPC-software some time ago and now have most of it saved on a drive.
I also gave Linux and OpenBSD a try, but I'm too unexperienced for both of them systems and couldn'd find any advantage compared to Tiger/Leopard except for some tinkering. (Edit: just reread
@wicknix 's Lubuntu-thread that causes some tickling in my fingertips to give Linux another try ...)
So fine-tuned TenFourFox/TenFourFoxBox (there's either
@eyoungren 's way for deeper insight or instant-karma), Webkit4Leopard, standard-Mail-App,
@wicknix 's TenFourTube/TenFiveTube and
@Dronecatcher 's knowledge of how to play video on PPC are the best of how to make the G4 book cope with current web/mail/streaming.
If you happen to prepare for DualBoot better start with Leopard in order to partition and prepare the drive, since Tiger/os9-drivers may cause problems, if you ever want to change partition-size, since a drive primarily partitioned with Tiger/os9-drivers might not allow repartitioning without erasing the partions (but certainly there are some tricks to get over this problem).