Spellbook's bottom-most section (the self-cost increasing) should say "during your turns." See Peddler, Destrier, and Fisherman. Janus' bottom section would be better worded as "during your turns, if your Journey token is face down, this costs
less."
Wording aside, there's a big issue with cost increasing effects like Spellbook: What happens if I play 4 Bridges and have one Spellbook in play? Do the 4 Bridges try to lower its cost to -
, instead reducing its cost to
, and then Spellbook raises its cost to
? Or does Spellbook raise its cost to
first and then the Bridges reduce its price to
?