I've just heard about a great resource for gamebook fans: thirty-one themes in the medium, from horror to SF to modern to non-fantasy. Duncan Thomson's (no relation to Jamie as far as I know) in-depth post covers hundreds of different gamebook series both classic and modern. Check it out on Rand Roll here.
And if you want to write your own gamebook, Stuart Lloyd has compiled an invaluable reading list to get you started. And trawling through some old posts here (such as this one) might also prove inspiring. I also find it useful to listen to Hieronymus J Doom's perceptive analyses of gamebooks on the Haunted Phonograph and Ed Jolley's Adventure Gameblog.
Talking of gamebooks, have you been keeping up with Prime Games' development reports on the CRPG version of Blood Sword? The latest concerns my favourite character class to write, the Trickster:
"The Warrior holds the line. The Enchanter bends the arcane. The Sage unveils hidden truths. The Trickster thrives where no one else dares -- in shadows, in whispers, in the thin places between honour and survival. Assassin, Knave, Hunter, or something in between, the Trickster proves that guile can be sharper than steel."
Read more about the Blood Sword CRPG and add it to your Steam wishlist here.